85027501 DC Power Systems Handbook

7/30/2019 85027501 DC Power Systems Handbook

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Table of Contents

The DC Power System 1

1.1 DC Power Overview 11.2 Rectifier 71.3 Battery 161.4 Distribution 271.5 Battery Return Bus 311.6 Supervisory and System Control 331.7 Low Voltage Disconnect Contactor 401.8 CEMF Cell 431.9 Battery Temperature Compensation 45

1.10DC - DC Converter System 511.11DC Power System Integration 541.12Inverters/UPS 58

Power System Sizing and Ordering 622.1 Calculations 622.2 Formulas 652.3 Power System Design Example 662.4 Ordering Information for Power Systems

and Loose Items 67

Site Engineering for DC Power 693.1 Site Layout and Loading 693.2 Grounding Network 713.3 Surge Protection Devices (SPDs) 743.4 Wiring 763.5 Engineering Drawings 80

Initial Installation 814.1 Safety Precautions 814.2 Tools List 83

4.3 Inspection 844.4 Power System Assembly/Mounting 85

4.5

Battery Installation 86

4.6 Cabling 894.7 Power Up Procedure 924.8 Battery Initial Charge and Discharge

Test. 944.9 Documentation 95

Power System Commissioning 97

Retrofit Installation 996.1 Precautions 99

6.2 Tools List 1006.3 Distribution Circuit Addition 1006.4 Common Ground Bus Addition 1006.5 Distribution Panel Addition 1016.6 Rectifier Addition 1036.7 Shunt Replacement 103

Maintenance and Field Repair 1057.1 Power System and System Controller 1057.2 RST Rectifiers 1077.3

RSM Rectifiers 109

7.4 Pathfinder 24-3kW, 48-3kW, and 48-

10kW Rectifiers 1127.5 CS and CSM Converters 1147.6 Vented Batteries 1167.7 Valve Regulated Lead Acid (VRLA)

Batteries 1187.8 Battery Failure; Detection, Prevention

and Corrective Action 119

Troubleshooting 1218.1 Power System and System Controller 121


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D C P O W E R S Y S T E M S H A N D B O O K

ARGUS TECHNOLOGIES 075-053-10 Rev D

CHAPTER

The DC Power System

The DC power system is a vital part of the communications network.

Most communication equipment, including PBXs, telephone switches,microwave transmission, fiber optic transmission, mobile radio, cellular,

etc. are designed to operate from a DC input voltage. A DC source has the

inherent benefit of higher reliability as compared to an AC source. This is

because the battery, which is often used for backup, is directly connected to

the load with no intermediate stage such as an inverter that may fail and

disrupt power to the load. The basic power system consists of a rectifier and

usually a battery, but may include various other components. The various

components are discussed in detail later in this section.

1.1 DC Power Overview

1.1.1 Typical DC voltage and current requirements

The two most common input voltage requirements for

communication equipment are +24V and -48V. The use of -48V is

rapidly becoming the most predominate as this is the maximum

safe working voltage according to both the National Electrical

Code (NEC) and the Canadian Electrical Code (CEC) that has no

current limiting requirements. The high voltage reduces the

current requirements making fuses/circuit breakers/cables smaller.

+24V evolved from the mobile radio industry, where equipment

was designed to operate from either an automotive (+12V)

charging system or a truck (+24V) charging system.


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ARGUS TECHNOLOGIES 075-053-10 Rev D 2

-48V evolved from the telephony world where 48 volts was

chosen because it was the maximum voltage that was considered

safe as technicians had to make live connections. The negative

polarity (positive ground, similar to the old British -6 VDC

automotive charging system) was chosen as it reduced the galvanic

corrosion that occurred when the lead sheathed telephone twisted

pair cables were originally deployed and buried in the earth.


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Load

LoadLoad

ACPowerOn

DC

DC

DC

ACPowerOff

Battery

Battery

AC

AC

DCPSB01A

Rectifier

Rectifier- -+ +

Load Load

Figure 1 Basic DC Power System Operation


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Table A Typical Telecom Equipment Voltage and Current Requirements

Application Voltage Current NotesMobile Radio BaseStation

+12 VDC


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Typical AC voltage sources

There are many different voltage sources around the world.

Identify the source that you are using and watch the rectifiers to

the source. See Table B.

Service Configuration LL Volts L-N Volts Where used? Notes

120/240V 1 PH3W

Single Phase 240 VAC 120 VAC USA, Canada

120/208V 3PH4W

Three PhaseWye

208 VAC 120 VAC USA, Canada

277/480V 3PH4W

Three PhaseWye

480 VAC 277 VAC USA

347/600V 3PH4W

Three PhaseWye

600 VAC 347 VAC Canada

208 V 3PH 3W Three PhaseDelta

208 VAC N/A USA, Canada

480 V 3 PH 3W Three PhaseDelta

480 VAC N/A USA

220/380 V3PH 4W Three PhaseWye 380 VAC 220 VAC EuropeAs iaSouth America

Table B Typical AC Commercial Voltage Sources

Figure 2 Single or Split Phase


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Figure 3 Three Phase Delta

Figure 4 Three Phase Wye or Star


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1.2 Rectifier

1.2.1 Description

The rectifier is a device that changes an AC (alternating current)

input to a regulated and filtered DC (direct current) output. The

DC output supplies power to the load (communication equipment)

and charges a backup battery if required.

1.2.2 Connection

The rectifier is connected in parallel with both the load and the

battery (if applicable). Multiple rectifiers may be connected

together in parallel, with their corresponding (+) and (-) leads

connected together.

1.2.3 Operation (Float charge mode)

The rectifiers are adjusted to the voltage requirement (float

voltage) of the battery and to share the load or supply the same

output current in systems with more than one rectifier.

AC-ON - The rectifier supplies current to the load and provides a

trickle charge current to the battery.

AC-OFF - The rectifier turns off and the battery will supply

current to the load until the battery is completely discharged.

AC-ON- The rectifier supplies current to the load, any extra

current available from the rectifier will be used to recharge the

battery.

1.2.4 Sizing details

The rectifier size is chosen by determining the most cost-effective

means of satisfying the total capacity requirements.

N+1 redundancy should always be considered. N isthe number of rectifiers required to satisfy the total

capacity requirements of the load and the 1 is an

extra rectifier added so that a failure of a rectifier in

the system will not jeopardize system integrity.


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Correct choice of either positive ground (-48VDC) or negative

ground (+24 VDC) is critical. The grounded potential is connected

to a common point and the live cable is connected through either

fuses or circuit breakers. Refer to power system design calculation

section.

1.2.5 Features and selection criteria

Low output noise/ripple ensures that the load is unaffected by

the rectifier in both battery and more importantly battery-less

operation. Note: the battery acts as a filter, but VRLA batteries

will fail prematurely when connected to rectifiers with high output

ripple voltage.

Tight voltage regulation (line and load) to ensure that the

battery is properly charged and the load does not receive

fluctuating voltages.

Modularvs. monolithic configuration; modular rectifiers allow

for easy replacement and expansion.

Unity power factor(P.F.>.95) is becoming more important as

the utilities move toward increased monitoring of power factor. A

poor power factor at your Telecom facility may result in the

electrical utility adding a surcharge to your electrical bill. InEurope, unity power factor is a CE requirement for Residential

and light commercial applications. North America may soon

follow this trend. There are two types of power factor

measurements displacement and true. The displacement component

of power factor is the ratio of the active power of the fundamental

wave (60 Hz), in watts, to the apparent power of the fundamental

wave in volt-amperes. This is the value used by utilities to

determine billing. True power factor is the ratio of the total power

input, in watts, to the total volt ampere input, this includes the

fundamental wave (60 Hz) and all the harmonics (120, 180, 240,

360, 480 Hz, etc. This value is used for efficiency calculations.

Early Argus rectifiers utilize passive power factor correction to

achieve reasonable power factor at low cost. The Pathfinder

rectifiers offered by Argus have a true power factor of >.99.


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Figure 5 Power in an Inductive Circuit

Figure 6 Power Factor Triangle

Low THD (total harmonic distortion) and damaging

harmonic currents to meet CE requirements and to eliminate

AC generator and transformeroverheating and interaction

problems. THD refers to the distortion of the incoming AC voltage

or current waveform when the rectifier is connected and is

expressed as a percentage.


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Three phase AC input - For higher power applications this

becomes more important to ensure even balancing of load on a

three-phase AC source.

High efficiency as well as having the obvious power savingsbenefit, reduces the size of the input feeder circuit breaker and

input cabling.

Wide AC operating window for both frequency and voltage to

tolerate fluctuations without the rectifier shutting down. Argus

rectifiers have a wide input tolerance range for both frequency and

voltage. This allows uninterrupted operation and also allows

universal operation for 208/240V 60Hz operation and 220V 50 Hz

operation with no modification or reconfiguration required.

Pathfinder 48-3kW & 24-3kW rectifiers (208/240 VAC I/P) will continue to

operate down to 90 VAC (with reduced output)!

Compact and lightweight helps reduce installation,

maintenance and shipping costs.

Balanced load sharing should be achieved between units of

the same design and with other types of rectifiers. Argus rectifiers

accomplish this with a combination of forced sharing

(master/slave) and/or adjustable slope regulation. Adjustable slopeallows you to tailor the voltage regulation characteristics of

different brands of rectifiers.

Forced sharing works by the rectifiers electing a

master unit (the rectifier with the highest output

voltage). The other rectifiers are forced to adjust their

output voltage to track the master and therefore share

the load.

Slope Regulation (Output Voltage) allows the user

to drop the output voltage of the rectifier a small

amount from no load to full load. This is done at a

fixed rate. The slope in the voltage regulation of the

rectifiers helps to allow the user to set the rectifiers to

load share easily and also allows you to tailor the

voltage regulation characteristics of different brands

of rectifiers.


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Figure 7 Output Slope Voltage Regulation and Current Limit

Adjustable current limit restricting output current of the

rectifier, in either a discharged battery or overload condition. The

rectifier can operate in this condition without damage.

Power limit allows the rectifier to supply greater output current

when the output voltage of the system is low. This reduces battery

recharge time and also provides greater overload capabilities

reducing the need for redundant rectifiers.

Figure 8 Current Output P 48/10 kW e/w Power Limit


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Figure 9 Power Limit (P 48-3kW) - Current Limit (RSM 48/50)

Comparison

A float/equalize mode selectorswitch allowing selection of

two operating modes:

1. Float mode for normal charging of the battery.

2. Equalize mode for boost charging (at a higher

charging voltage) of batteries when required. This

boost charging eliminates any sulfation on the

battery plates resulting in cell voltage imbalances

and poor performance. This is an important feature

for vented lead calcium batteries floated at

reduced voltage levels. Typically not required

with VRLA batteries under normal operating

conditions.

Automatic high voltage shutdown (HVSD) or over-

voltage protection (OVP)to switch the rectifier off in case of

a high output voltage condition, preventing damage to the batteries

and load. An automatic restart feature should be included in the

event that a site temporary abnormality surge as a ground surge

resulted in the HVSD.


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Soft-start gradually steps each rectifier on-line at power up. This

eliminates start-up current surges associated with many rectifiers.

The feeder breaker and feeder size requirements are decreased,

reducing the installation costs of the rectifier.

Adjustable delay start allows staggered start-up of rectifiers

reducing stress on the AC generator and also allows the rectifiers

to be started after the site air conditioner compressor (drawing

high surge current) has started.

Alarms provide indication of rectifier failure and should be of

fail safe design. Local indication plus remote relay contacts are

required.

Remote sensing leads are connected directly from the battery

to the rectifiers via a sense fuse distribution panel located in the

supervisory panel. This allows the charger output voltage to be

regulated at the battery improving voltage regulation at the

battery. This is important with power systems that incorporate

separate charge and discharge circuits or power systems where

there may be a significant voltage drop in the battery cables. If

this feature is not connected, the rectifiers automatically revert to

internal sensing, regulating the rectifier output voltage to the

rectifier output terminals.

Remote Control and Monitoring allows the rectifiers to be

remotely controlled and monitored from a central supervisory and

control panel.

Model Voltage Current Features

Pathfinder 24 VDC 18, 50,100 A Convection or fan cooled

RSM 48/10 48 VDC 10, 30, 50, 180 A Modular design

200 kHz resonant converter design

RSM 24 VDC 7.5, 50,100 A Convection or fan cooled

48 VDC 15, 30, 50, 100 A Modular design

100 kHz forward converter design

Passive power factor correction

RST 12 VDC 50, 100 A Convection cooled24 VDC 30, 50, 100 A Monolithic Design

48 VDC 15, 30, 50, 100 A 48 kHz forward converter design

Passive power factor correction

Table C Argus Technologies Solutions


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1.2.6 Theory of Operation RSM 24/50, 24/100,48/30 and 48/50

Please refer to the power circuit block diagram. The 184-264 VAC

50/60 Hz input is fed through a circuit breaker into a full wave

rectifier, which provides a 120 Hz 340 V peak pulse train to aninput filter circuit. The input filter provides a nominal 290 volts

DC "raw supply" with approximately 30 VP-P 120 Hz ripple to the

transistor switching circuit.

The transistor switching circuit chops the raw supply into

nominally 525VP- P, 100 kHz rectangular waveform with a nominal

66% duty cycle. This waveform is fed into a ferrite power

transformer, which steps down and isolates the high frequency

switching waveform. A rectifier circuit converts the power

transformer output to a DC pulse train of nominally 136 V peak. A

two-stage output filter averages and smoothes this pulse traindown to provide the nominal 52 VDC output with low noise.

A voltage error amplifier circuit senses the output voltage and

compares it with the voltage reference to provide a voltage error

signal. Similarly, a current error amplifier senses the output

current using a shunt resistor and scaling amplifier to compare the

output current to the desired maximum output current to provide a

current error signal.

These signals are fed into the pulse width modulator (PWM) via

OR-ing circuitry so that either voltage or current regulation is

achieved. The pulse width modulator controls the "ON" time of the

switching transistors to vary the output as commanded by the error

amplifiers. It also senses the switching transistor current on an

instantaneous basis to provide cycle-by-cycle protection of the

switching transistors. An auxiliary supply, powered via a small

50/60 Hz transformer, and a DC/DC converter power the control

circuit and front panel circuitry. The PWM receives the ON/OFF

command and clock signal from the front panel circuit and control

circuitry.


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FrontPanelCircuit

MicroProcessor

InputRectifier

Input185-26

5VAC

50/60Hz

60Hz

120Hz

525V

250V

136V

0V

52V(48VUnits)

290VDC

100kHz

+3

40V -3

40V

O

V

Auxiliary

Supply

Local

Current

Sense

O

utput

V

oltage

S

ense

Output

Current

Sense

PulseWidthModulator

(PWM)

Input

Filter&

Storage

Capacitors

Transistor

Switching

Circuit

Outpu

tRectifier

Isolation

Boundary

Transistor

Drive

DC/DC

Current

Error

Amplifier

Voltage

Error

Amplifier

Output

Filter

Shunt

OrGate

V INAU

X

IOut

Voltage

Reference

Current

Reference

-Adjustments

-Display

-Monitoring

VO

ut

Communication

On/Off

C

ommand

Output

RemoteSense

DCPSH07A

-

-

+

+

Figure 10 RSM Block Diagram


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1.3 Battery

1.3.1 Description

The battery is an electro-chemical means of energy storage. When

AC power is interrupted to the rectifiers or when there is

insufficient current available from the rectifiers to support the

load requirements, the battery will automatically supply current to

the load. The battery may be used in combination with a generator

to provide back-up power for extended time periods to the load. A

battery consists of a series connection of multiple cells. The

number of cells in series is determined by the operating voltage of

the system and the operating voltage of each cell.

1.3.2 Connection

The battery is connected in parallel with the rectifier and the load.

1.3.3 Operation

As detailed in the rectifier operation section.

Some batteries may require periodic equalization. Equalization is

where a higher boost voltage is applied to the battery to ensure the

proper cell voltage balance and correct conditioning of the battery

cells.

Parameter Valve Regulated Lead Acid Battery (VRLA) Flooded or Vented Battery

One Cell 24 V System 48 V System One Cell 24 V System 48 V System

Nom. V 2 24 48 2 24 48

Float V 2.25 27 54 2.20 26.4 52.8

Equalize V 2.30 27.6 55.2 2.30 27.6 55.2

End V 1.75 21 42 1.75 21 42

Op. Win. V 1.75-2.30 21-27.6 42-55.2 1.75-2.30 21-27.6 42-55.2

# cells 1 12 24 1 12 24

Table D Typical battery operating parameters

1.3.4 Sizing details

Determine your load profile (i.e. amps per hrs) and select the

battery using the manufacturers sizing table (See: Table E).

Batteries are rated using the following criteria:

Temperature (25 deg C in North America, 20 deg C

in Europe).


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Endvoltage (the lowest voltage that the cell is

discharged down to). The end voltage used in

calculations is usually the minimum voltage that the

battery can be discharged down to without damage. A

more conservative end voltage will increase the life

expectancy of the battery but reduce back up time.

Refer to IEEE battery sizing guidelines for calculating battery size for complex

load profiles Evaluate battery charge rate for sizing intercell and inter-tier

connectors

Apply temperature performance correction factor for average

temperatures below 25 deg. C, (77 deg. F), if applicable (See:

Table F).

Ensure that the battery operating voltage coincides with the

acceptable operating voltage window for the equipment connected.

Apply the beginning and end of life de-rating factor. This factor is

20% and allows for:

The battery shipped at less than 100% capacity,

typically 90% (Full capacity is achieved after a short

period of float service).

Cells that are tank formed ship at 100 % capacity.

Battery end of life considered as 80% of capacity

(See: Figure 11).

Battery capacity is determined by the number & size of the plates,

therefore the larger the battery the greater the capacity.

Battery strings may be connected in parallel to obtain additional

capacity. Strings should be equal in capacity and interconnecting

cables should be of approx. the same size and length to obtain

optimum charge and discharge characteristics. The maximum

recommended number of parallel strings is three.


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Smaller applications commonly use mono-block batteries. Mono

blocks are batteries that have more than one cell contained in the

assembly (i.e. an automotive battery is a 6 cell 12 VDC mono-

bloc).


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Average Cell Performance Data*

Discharge rates in amperes.

1.215 SP. GR. ELECTROLYTE AT 77 (25C), INCLUDING CELL CONNECTORS

TYPENOM.A.H.CAP.

72HR.

24HR.

12HR.

8HR.

5HR.

4HR.

3HR.

2HR.

1.5HR.

1HR.

30MIN.

15MIN.

1MIN.

TO1.50VPC1 MIN

To 1.75 VPC Final

EA-5 230 4.6 11.1 18.8 26.6 44.0 49.9 59 75 87 102 152 197 290 530

EA-7 270 4.8 12.9 23.7 33.3 49.0 58.5 73 98 120 154 226 291 426 790

EA-9 350 6.4 17.2 31.6 44.4 65.3 78.0 97 131 160 205 298 380 548 1010

EA-11 440 8.0 21.5 39.5 55.5 81.7 97.5 122 164 199 257 367 465 685 1270

EA-13 530 9.6 25.8 47.4 66.6 98.0 117 146 197 239 308 435 558 792 1460

EA-15 620 11.2 30.1 55.3 77.7 114 137 171 229 279 359 507 651 924 1700

EA-17 710 12.8 34.4 63.2 88.8 131 156 195 262 319 411 571 728 1010 1870

EA-19 800 14.4 38.7 71.1 99.9 147 176 219 295 359 462 634 801 1100 2030

EA-21 890 16.0 43.0 79.0 111 163 195 244 328 399 513 694 870 1190 2200

*Rates shown depict average values and are subject to IEEE-485

CONSTANT CURRENT DISCHARGE RATINGS AMPERES @ 77FOperating Time To End Point Voltage

EndPointVolts/Cell

5min.

15min.

30min.

60min.

2hr.

3hr.

4hr.

5hr.

6hr.

7hr.

8hr.

10hr.

12hr.

20hr.

24hr.

48hr.

72hr.

10hr

1.75 274 162 105 61.5 34.8 25.0 19.6 16.2 14.0 12.3 11.0 9.08 7.79 5.00 4.19 2.13 1.43 1.0

1.80 240 151 99.0 60.1 34.0 24.2 19.0 15.8 13.6 11.9 10.7 8.80 7.58 4.89 4.10 2.10 1.42 1.0

1.85 203 136 92.0 55.0 31.4 22.8 18.0 15.0 12.9 11.3 10.1 8.44 7.23 4.67 3.92 2.02 1.37 0.9

1.90 156 110 75.0 47.0 28.9 21.0 16.8 14.0 12.0 10.6 9.50 7.90 6.73 4.34 3.65 1.88 1.26 0.9

Table E Typical Battery Performance Table


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Electrolyte C Temperature F Cell sizecorrection factor

-3.9 25 1.520

-1.1 30 1.430

1.7 35 1.3504.4 40 1.300

7.2 45 1.250

10.0 50 1.190

12.8 55 1.150

15.6 60 1.110

18.3 65 1.080

18.9 66 1.072

19.4 67 1.064

20.0 68 1.056

20.6 69 1.048

21.1 70 1.04021.7 71 1.034

22.2 72 1.029

22.8 73 1.023

23.4 74 1.017

23.9 75 1.011

24.5 76 1.006

25.0 77 1.000

25.6 78 0.994

26.1 79 0.987

26.7 80 0.980

27.2 81 0.976

27.8 82 0.972

28.3 83 0.968

28.9 84 0.964

29.4 85 0.960

30.0 86 0.956

30.6 87 0.952

31.1 88 0.948

31.6 89 0.944

32.2 90 0.940

35.0 95 0.930

37.8 100 0.910

40.6 105 0.890

43.3 110 0.880

46.1 115 0.870

48.9 120 0.860

Table F Temperature Performance Correction Factor TableThis table is based on flooded le ad-acid cells only.


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For further information, please refer to:

IEEE-485-199 - IEEE recommended practice for

sizing large lead-acid batteries for stationary

applications.

IEEE-1184 - IEEE guide for the selection and sizing

of batteries for uninterruptible power systems.

IEEE-1689 - IEEE guide for the selection of valve-

regulated lead-acid (VRLA) batteries for stationary

applications.


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Figure 11 Battery Performance vs. Time


There are three main types of lead acid batteries that are used in

telecommunication applications. The three types, based on acid

classification, are listed below.


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Acid Classification

Description Advantages Disadvantages

Flooded Technology free liquid electrolyte, similar to an

automotive battery

-proven technology

-flat, tubular, plant options -bestlife expectancy of lead acidbatteries at higher operatingtemperatures

-high maintenance

-transportation restrictions

VRLA-AGM(Absorbed GlassMat) Technology

a small quantity of liquidelectrolyte is held in suspension inthe fiberglass mat

-low maintenance-minimal vented gasses-easy installation in any position-easier shipping classification-will not freeze

-difficult to evaluate battery stateof health-rapid reduction of life expectancwhen operated at hightemperatures (above 25 deg C)

VRLA-GelTechnology fumed silica is added to gel theliquid electrolyte -lasts longer than AGM at highoperating temperatures -performance (AH per kg) is lessthan AGM battery

Table G Battery Type Comparison


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Figure 12 Battery Construction


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Cycling requirement - different cell plate alloys and plate

configuration affect the cycling (charge and discharge)

performance of the battery. Determine the cycling requirement of

your application (i.e. float with light cycling, float with heavy

cycling and full cycle service) and choose the correct battery for

the application.

Rate of discharge:

High < 15 minutes

Medium 15 min. - 2 hr.

Low 2 hr +

Maintenance requirements.

Physical design parameters, ventilation, floor loading,available space.

Costincluding life expectancy.

VRLA batteries of both AGM and gel type are usually the first

choice for backup. Some of the important features to look for in

a VRLA battery are:

Jar material with low water vapor diffusion rate i.e.

polypropylene or PVC to prevent dry out.

Flame retardant jar materials. Even compression of plates through a fixed method of

jar compression to maintain, plate to microporous

separator integrity (AGM).

Designed to prevent strap corrosion and lug corrosion

(AGM).

The Battery may be packaged on a traditional battery stand or be

of bolt together self supporting construction. For smaller battery

strings the use of relay rack shelves or cabinets is a consideration.

There are also AGM batteries available from the manufacturesprepackaged for easy installation into a relay rack.

1.3.6 Argus Technologies Solutions

Argus does not manufacture batteries, but will provide batteries as

part of the integrated power system.


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DCPSB02A

Rectifier#2

Rectifier#1

Charge(-)

Circuit

Breaker

Distribution

Battery

- -+ +

Charge(+)

ShuntBar

Termination

Panel

Load

GroundBar

Load

Figure 13 Basic System e/w Distribution


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1.4 Distribution

1.4.1 Description

Fuses and circuit breakers are used to safely distribute the DCpower from the rectifier and battery to the loads. These devices

protect the loads and load cables from short circuits, overload

conditions and allow easy manual shutoff . This helps to isolate

faults between circuits. Circuit breakers and fuses are also used

for protecting the battery and battery cables and to allow an easy

means of disconnecting the battery from the system for safety, fire

prevention and maintenance.

1.4.2 Connection

Primary DistributionLoad fuses or circuit breakers located at the power system are

connected in series between the power system and the loads and/or

between the power system and the battery.

Secondary Distribution

Large main fuses are installed in the power system to distribute dc

power to remote BDFBs (Battery Distribution Fuse Boards) or

BDCBBs (Battery Distribution Circuit Breaker Boards). From the

BDFB power is distributed to the loads with smaller individual

circuit breakers.

1.4.3 Operation

Fuse

Excessive current flowing through the fuse melts the internal link,

disconnecting the load from the power system. A guard fuse is

connected in parallel with the main fuse and will blow when the

main fuse blows. The guard fuse provides a local indication and

also will send an external alarm signal via a built-in contact.

Circuit breaker

Excessive current flowing through the circuit breaker causes

excessive heat (thermal) or an excessive magnetic field (magnetic)

to trip the circuit breaker to the off position. Alarm sending is via

breaker auxiliary contacts or electronic trip detection circuitry.


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Electronic trip detection circuitry

A 10 000 ohm bypass resistor is connected across the circuit

breaker (to limit current) and the output voltage of the circuit

breaker is monitored. The benefit of the circuit is that an alarm is

indicated only when a breaker is off with a load connected and no

connection to the auxiliary contacts is needed.

Breaker ON with no load voltage on breaker

output is high no alarm.

Breaker ON with load voltage on breaker output is

high no alarm.

Breaker OFF with no load voltage on breaker

output is high (due to bypass resistor) no alarm.

Breaker OFF with load voltage on breaker output

is low (due to load forcing voltage down to zero V)

alarm is indicated.

Voltage will be measured on the output of a circuit breaker even when the

breaker is off, however current flow is limited to a few mA due to the 10,000

ohm resistor.

Sizing

Most communication equipment requires fuses or circuit breakers

with short delay curves fast blow to provide proper protection

Fuses with different curves may be utilized to match specific load

requirements.

Load fuses and circuit breakers should be sized 1.25 to 1.5 times

the maximum continuous anticipated load on the circuit for

reliable operation.

Battery fuse/circuit breaker should be sized at 1.25 times themaximum current rating of all the rectifiers in the system

(minimum).

Ensure that the current capacity of the circuit breaker panels is not

exceeded by the current draw of the connected loads.


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The interrupting capacity (highest fault current that the device is

rated to safely interrupt) of the protection device should match the

application. Battery protection devices require higher interrupting

capacity due to the high short circuit current capability of a

battery and the large cables (low impedance).

Features and selection criteria

Remote alarm sending via guard fuse or remote

contacts on circuit breaker.

Alarm indicating lamp and an isolating relay.

Traditional bolt-in, plug-in or snap-in circuit

breakers.

Guard bars to prevent accidental tripping of circuit

breakers.

Electronic breaker trip detection circuitry.

Various types of fuses and circuit breakers can be

combined in different panels to meet load requirements.

Current monitoringvia series shunts to ensure circuits

are not overloaded or power consumption monitoring for

billing purposes.

Battery protection features:

EPO - Emergency Power Off control capability

using contactor or shunt trip breaker for locations

that require a mandatory emergency power

shutdown to meet local fire codes.

LVBD - Low Voltage Battery Disconnect control

capability to automatically disconnect and

reconnect the battery during an extended ac power

outage.

Manual battery disconnection - Single string

disconnection for maintenance and fault isolation.


34/141



Fuses or circuit breakers?

Fuse advantages - high interrupting capacity,

cost, flexibility, fast speed.

Circuit breaker advantages - can be reset,

accuracy, low speed.

1.4.4 Argus solutions

Fuse blocks:

Type Rating-Range (block size)

GMT 0-15A

70 Type 1/2A used for indicating purposes

BAF 0-30A

Cartridge 0-30A, 31-60A, 61-100A, 101-200A

TPL 61-800A

Breakers:

Manufacturer Type Rating Interrupting Capacity Usage

Heinemann AM 5 - 100 A 5 or 10kA Load or battery

Heinemann CD 5 - 100 A 10,000A Load or battery

Heinemann GJ 100-700 A 25,000A Load or battery


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1.5 Battery Return Bus

1.5.1 Description

The battery return bus (BRB), also referred to as the

common ground bus, provides a common return/reference

point for the connected loads and the power system. This common

reference point is connected to the site ground to provide a low

impedance path to ground for transients and noise.

1.5.2 Connection

The ground lead of all DC load inputs, batteries and rectifiers

should be connected to this point. This bus must also be connected

to the site ground grid (see grounding network section).

1.5.3 Sizing

Ground bars are sized according to load requirements.

1.5.4 Features

Allowances for termination oftwo-hole lugs of

various sizes should be provided.

Ground bars must be isolated from the relay rack

through glastic insulators so that the power system can

be integrated correctly into the site single point

ground network.

Provisions for small cable termination shall also

be provided.

Tin-plated copper construction for corrosion

resistance.


Various types are available from Argus including flat bars and U

shaped bars for additional cable termination.


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DCPSH03A

APower

Superviso

ryPanel

GroundBar

Charge(-)

Battery

- -+ +

Charge(+)

ShuntBar

T

ermination

Panel

Rectifier#2

Rectifier#1

V

Load

Shunt

Circuit

Breaker

Distribution

Figure 14 Basic System e/w Supervisory Panel


37/141



1.6 Supervisory and System Control

1.6.1 Description

In most power systems it is desirable to have a central control andmonitoring panel to provide local and remote indication of system

operating parameters and alarms and also to provide system

control.

1.6.2 Connection

Various connections are made to the supervisory panel from

different components so that different parameters and levels may

be monitored and controlled.

Shunts can be installed in the grounded or live load, battery or

system conductor.

1.6.3 Operation

The battery (charge) and load (discharge) voltage is monitored

with a direct connection of the sense leads to the source; battery or

load.

The battery (charge) and load (discharge) current is monitored

with an external shunt. Shunts are calibrated low resistance

resistors designed to provide a specific voltage drop at a specific

current (linear relationship). This voltage drop is measured by the

ammeter. A typical shunt rating would be 200A, 50mV. Therefore

200 amps of current flowing through this shunt will cause a

voltage drop of 50mV.

Calculated values may also be displayed such as total rectifier

output current (numerical addition of individual rectifier output

currents). In systems where there is no battery shunt an estimation

of battery current can be calculated by subtracting the discharge

current from the rectifier total output current.

Room and battery temperature can be monitored with temperature

probes.

Additional analog parameters can be monitored using available

inputs.


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Events such as distribution fuse alarm, battery fuse alarm, rectifier

failure, converter failure, etc. are monitored by the supervisory

panels.

Alarms are based on an analog or digital event. Each alarm has atwo to five second delay before extending an alarm. The delay

eliminates false triggering due to line transients or false alarms.

Analog alarms usually incorporate a hysteresis into the trigger

level to prevent oscillation of an alarm condition caused by a level

fluctuating around the set point. Alarm functions provide both

local (visual and audible (optional)) and remote (relay contact)

indicators.

Relay contacts may be configured as form A (NO), form B

(NC), or form C (NO & NC).

Control functions are extended from the supervisory panel to

control various other power system components.

Microprocessor based supervisory panels have direct

communications with rectifiers for monitoring and single point

control. Communications is via RS-485 connection.

1.6.4 Sizing

Shunts are sized according to load requirements and limit the

initial capacity of the power system. Current flowing through ashunt must not exceed 80% of its nominal rating on a continuous

basis.

1.6.5 Features (panel dependent)

Typical Alarms

high/low voltage (1 & 2)

AC mains high/low/failure

distribution fuse/breaker

battery fuse/breaker

control fuse trip

rectifier failure alarm minor (one rectifier)

rectifier failure alarm major (>one rectifier)

converter failure alarm minor (one converter)

converter failure alarm major (>one converter)

auto-equalize


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high voltage shutdown

low voltage disconnect

CEMF (out)

CEMF (fail)

rectifier communication lost Power system minor alarm (logical or-ing of various

non critical alarms)

Power system major alarm (logical or-ing of various

critical alarms)

etc.

Controls

Control features are used to control power system devices such as

rectifiers and contactors.

Manual equalize - Allows the user to initiate all the rectifiersinto the equalize mode with one common switch. Used for

maintenance purposes with VRLA batteries, i.e. equalizing cell

voltages in a battery string.

Auto-equalize - Common in applications where flooded batteries

are deployed. This function initiates the rectifiers into the equalize

mode (boost charge) for a preprogrammed amount of time

(duration). It is used with vented batteries floated at low voltages

to prevent lead plate sulfation or where a quicker recharge of the

battery is required after a power failure. Auto-equalize is initiated

in one of three ways:

1. after power failure based on the voltage of the

battery;

arm voltage (indicating that a long outage has

occurred, rectifiers are off and the batteries have been

discharged) and

activate voltage (indicating the battery is nearing

full charge and the equalize mode is triggered,

rectifiers are on) The rectifiers will remain in the

equalize mode for the duration.

2. periodic equalize; where the batteries are

equalized at the interval programmed in days.


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3. manual initiation using the duration setting to

return the rectifiers to float after the duration has

expired.

HVSD/OVP - automatically shuts down all the rectifiers when anoutput DC over-voltage condition is detected.

LVD - controls 1 or more contactors that automatically open when

a low battery voltage condition is detected and close when the

battery voltage returns to normal. See LVD section.

LVD override control - switch for maintenance.

Battery temperature compensation is used to adjust the

rectifier output voltage to ensure that the battery float voltage is

correct for the operating temperature of the battery. See batterytemperature compensation section.

Charge current control is used to limit the flow of current into

the battery when recharging commences after a power failure. It is

programmed typically at C/5 (capacity of the battery/5). This

ensures that the battery is not charged too quickly, resulting in

excess heat generation and possible reduction in battery life. This

can be very important for VRLA type batteries.

Battery diagnostics

Battery capacity estimation - the capacity of the

battery at the current point in time expressed as a

percentage of the battery manufacturer's specification.

Battery state of health estimation - a continual

measurement of the batteries performance and state of

health. It is expressed as a percentage of the

manufacturer's specification. Alarm triggers can be set

to alarm when the battery state of health falls below

80%.

Battery run time prediction - the algorithm

predicts the number of hours that the battery will last,

before the battery will be fully discharged or a LVD

will occur, at the present discharge rate.


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Rectifier group single point adjustment - allows the

operator to setup and adjust all the rectifiers at one central

location.

CEMF (counter-electro-motive-force) controls 1 or morecontactors that automatically close when a high load voltage

condition is detected and open when the load voltage returns to

normal or is in a low voltage condition. See CEMF section.

1.6.6 Other Features

VAR (Visual alarm reset) - Is used to clear visual alarms.

Lamp test - Illuminates all lamps to verify operation.

Test - Combined with an external power supply, allows the userto test and calibrate the power system while in service (SD series

only).

ALCO (Alarm Cutoff) - Is provided to clear the relay contacts

and audible alarm associated with each alarm condition this allows

extended alarms to be canceled while alarm condition is being

resolved by local personnel.

1.6.7 Advanced features (SM series)

Remote access for control and monitoring,LocalRS232

Remotedial-in

Remotedialback

SNMP (Simple Network Management Protocol) alarm

reporting over network LAN or WAN

History and statistics

Programmable alarm relays

LCD display of alarms, parameters, etc.


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1.6.8 Argus Solutions

SM02

This microprocessor based supervisory panel combines a large

LCD display and keypad with optional modem card to provide

advanced power system monitoring and control features.

SM03

This microprocessor based supervisory panels provides many of

the features of the SM02 (without the remote access) in a smaller,

reduced cost package.

SD02 & 04

These discrete component supervisory panels provide

comprehensive metering, control and alarm functionality.

SD03 & 05

These discrete component supervisory panels provide basic

metering, control and alarm functionality.


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DCPSH04A

APower

Superviso

ryPanel

Charge(-)

Battery

- -+ +

Charge(+)

ShuntBar

V

Load

Circuit

Breaker

Distribution

LowVoltage

Load

Disconnect

GroundBar

T

ermination

Panel

Rectifier#2

Rectifier#1

Shunt

Figure 15 Basic System e/w Load Disconnect


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1.7 Low Voltage Disconnect Contactor

1.7.1 Description

The low voltage disconnect (LVD) contactor is used to disconnecteither the load from the system (load disconnect) or the battery

from the system (battery disconnect) when the battery has been

completely discharged in a long duration power outage. There are

three reasons for using a LVD:

1. Prevention of load damage due to an under voltage

condition. Some communications equipment may

be damaged when operated with an excessively

low input voltage or draw excessive current that

could trip a feeder circuit breaker.

2. Prevention of damage to the battery due to over-

discharge. Discharging a battery below the lowest

recommended end voltage (see battery section)

might permanently damage the battery.

3. Load shedding - to disconnect specific loads in a

prioritized sequence to maximize backup time for

more critical loads (ex. up to three individually

controlled contactors can be used with the SM02).

1.7.2 Connection

The low voltage disconnect can be connected in series with the

load (load disconnect) or in series with the battery (battery

disconnect).

The LVD is controlled by the supervisory panel.

1.7.3 Operation

The supervisory panel continuously monitors system voltage.

After an extended AC outage the batteries will discharge down to

the disconnect point. The disconnect point is typically set to the

lowest acceptable battery discharge voltage (end voltage). In a

Telecom application the end voltage typically used is 1.75 volts

per cell (21 VDC in a 24 VDC system and 42 VDC in a 48 VDC


45/141



system). When the disconnect point is reached the load or battery

will be disconnected from the system.

The load or battery will remain disconnected until AC outage is

over. On return of AC a load disconnect and a battery disconnectsystem function differently (see below).

Load disconnect The rectifiers will pre-charge the

batteries for a few minutes until the battery voltage

reaches the reconnect point (typically 25 VDC or 50

VDC). When the reconnect point is reached, the load

is connected on line at this voltage level.

Battery disconnect Immediately after the

reapplication of AC, the load will see a slowly

increasing DC voltage (0-50 VDC over an 8-10 secondperiod, due to the soft start feature in the rectifier). At

the 50 VDC point the battery will be connected on

line.

A wide voltage differential between the in and out settings (i.e.

out 42V, in 50 V in a 48V system) prevents the contactor from

oscillation because the battery voltage will naturally rise after the

load has been removed from it and reconnection without the

rectifiers on-line would not be desirable.

Load vs. battery disconnect - In some cases battery, insteadof load, disconnection is desirable. The advantage of this system is

that an accidental operation of the LVD will not disrupt power to

the load unless the AC is also off. The disadvantage of the battery

disconnect that the load will see a slowly increasing input voltage

0-50V as the rectifiers perform the soft start this may cause

damage to the load or inadvertent fuse or circuit breaker tripping.

Careful evaluation of the load specifications is required to verify

that this method of disconnection will not affect the load.

1.7.4 Sizing

Low voltage disconnect contactors are available in various sizes.

The rating of the LVD indicates its maximum current

carrying/switching ability.


46/141




Able to switch high current loads reliably.


200A, 800A and 1200A available.


47/141



1.8 CEMF Cell

1.8.1 Description

The CEMF cell is a diode array that is connected in series between

the power system and the loads. A contactor is installed in parallel

with the diodes. The diodes are used to reduce the voltage applied

to the loads by a fixed value during normal operation or when the

batteries are equalize charged. The contactor automatically

bypasses the CEMF when the system is on battery to maintain

maximum backup time for the loads.

CEMF cells are rarely used in modern telecommunications systems

as they introduce step voltage changes to the load voltage when

switched in or out that may affect load operation. It alsointroduces another single point of failure.

It was historically used with both step by step and crossbar

telephone switching offices.

A common alternative to the CEMF cell is to remove one battery

cell from the string and lower the rectifier output voltage to reduce

the operating voltage of the system; for example: 23 cell system

with VRLA batteries 23 x 2.25 V per cell = 51.75V.

1.8.2 Connection

The CEMF cell is connected in series with the load.

The supervisory panel controls the CEMF cell.

1.8.3 Operation

The supervisory panel continuously monitors system voltage.

There are two scenarios for CEMF use:

1. CEMF cell normally IN to reduce load voltagein the float and equalize mode. The normal system

float voltage is above the IN setting of the CEMF

cell the CEMF contactor is opened so that current

flow is through the CEMF diodes and the load

voltage is reduced. When a power failure occurs


48/141



and the voltage drops the contactor is closed to

increase the voltage at the load to ensure

maximum back up time. When power is restored

the contactor will open when the voltage returns to

normal diverting current through the diodes andreducing the load voltage.

2. CEMF cell normally OUT to reduce load

voltage in the equalize mode only. In this system

the IN setting of the CEMF is set higher than the

float voltage and the contactor normally bypasses

the diodes. When equalize mode is selected the

voltage rises above the IN setting and the

contactor is opened, current flows through the

diodes and the voltage at the load is reduced.

When the rectifiers are returned to float mode the

voltage drops below the out setting and the diodes

are again bypassed by the contactor and the load

voltage returned to normal.

1.8.4 Sizing

Voltage drop required.

Current required by load.

1.8.5 Features

Monitoring of cell status.

Alarm on failure of cell.


Cells and contactors in various sizes are available.


49/141



1.9 Battery Temperature Compensation

1.9.1 Background

Battery performance and life expectancy is directly related to the

battery ambient temperature. The optimum temperature fo r battery

operation is 25 deg. C (77 deg. F). Above this temperature, battery

life is compromised and below this temperature battery

performance is reduced.

VRLA batteries have a negative characteristic called thermal

runaway. This occurs when the internal temperature of the battery

rises due to overcharge, high ambient temperature or internal fault.

The rise in internal ambient temperature causes the battery to draw

more float current which in turn elevates the internal batterytemperature. This cycle continues until the battery fails. The

failure of the battery may be quite dramatic.

1.9.2 Description

Temperature compensation is the process of automatically

reducing the charge voltage applied to the battery at high

temperature (to increase life and prevent thermal runaway) and

increasing the voltage applied to the battery at low temperatures

(to increase the battery capacity and to ensure correct charging of

the battery).

1.9.3 Connection

Connection is as follows:

1. Traditional rectifiers with non-SM supervisory

panels use a temperature compensator module

(TCM) connected in series with the rectifier

remote sense line input and the battery that

requires temperature compensation.

2. Smaller rectifier systems (i.e. RSM 48/7.5 and

48/10) have this feature built in; there are no

additional sense/battery connections required.


50/141



3. RSM/Pathfinder rectifiers with SM supervisory

panels, require no additional sense/battery

connections.

Temperature probes (1-4) are mounted directly to either the samebattery negative termination post or to multiple negative posts to

monitor multiple battery strings.

1.9.4 Operation

Operation is as follows:

1. Non-SM based systems, the TCM adjusts the

output sense voltage to the rectifiers based on

ambient temperature detected at the battery. The

rectifiers will adjust their output voltage accordingto the sense voltage level detected at their remote

sense input. (See Table H & I)

2. Small systems adjust the rectifier output voltage

based on ambient temperature detected at the

battery. (See Table H & I).

3. SM based systems, the SM will automatically

adjust the rectifier float voltage based on the

battery temperature detected. It will repeat this

process at the interval programmed. The rectifierRS 485 communications link is used for this

purpose.

At 25 deg. C (77 deg. F) no voltage compensation will occur.

At temperatures below 25 deg. C, the rectifier will increase its

output at a fixed rate(ex. -2.5 mV per cell per deg. C change from

25 deg C reference).

At temperatures above 25 deg. C, the rectifier will decrease its

output at a fixed rate(ex. -2.5 mV per cell per deg. C change from

25 deg C reference).

To prevent excessive voltage from damaging the load, the battery

or causing a high voltage alarm condition; the battery voltage

maximum compensation may be limited (lower break point) at a

fixed temperature (ex. 0 deg C).


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To prevent excessively low voltage from undercharging the battery

or discharging the battery; the battery voltage maximum

compensation may be limited (upper break point) at a fixed

temperature (ex. 50 deg C).

1.9.5 Sizing

Temperature compensation slope

Match the compensation slope to the recommendations of the

battery manufacturer. Default to conservative 2.5 or 3.5 mV if this

information is unavailable.

Breakpoint

The selection of the breakpoint is critical. This determines the

maximum and minimum voltage that will be applied to the batteryand the load. Match the breakpoints to the recommendations of the

battery manufacture. Carefully select the lower breakpoint as this

determines the maximum voltage applied to the load.

Check load acceptable input voltage operating window; for example: a 4.5 mV

slope with a -40 deg C breakpoint in a 48V system will result in 61 volts applied

to the load in a low temperature condition.

1.9.6 Features and selection criteria Fail detection circuitry.

Redundant temperature probes for increased safety.

Automatic turn off if a fault is detected and an alarm

extended.


TCM

This external temperature compensation module can be either

relay rack or surface mounted. It will operate with RST (6 max.)and the larger remote sense input equipped RSM rectifiers (6

shelves max.). It will also operate with non-Argus remote sense

input equipped rectifiers.


52/141



TCM Internal

This feature is available built into Argus non-sense line equipped

rectifiers, including RSM 48/7.5, RSM 24/15 and RSM 48/10.

SM System Controllers

Control larger RSM rectifiers and pathfinder rectifiers through the

communications link.


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Table H 24 Volt Temperature Compensated Battery Float Voltage

These tables are provided as a guideline only. If battery

temperature falls between values on the above scale,

estimate the voltage setting based on the closest numerical

values.

* Refers to ambient temperature at the battery terminal

posts.

** BFV refers to Battery Float Voltage Check battery

manufacturer's recommended settings.

*** Refers to Nominal Battery Temperature. This is theoptimum temperature for battery operation. No compensation

occurs at this temperature (use as a reference point).

TEMPERATURE* BFV**=27.00V BFV**=27.25V BFV**=27.50V

C F @25C(77F) @25C(77F) @25C(77F)2.5mV(volts)

3.5mV(volts)

4.5mV(volts)

2.5mV(volts)

3.5mV(volts)

4.5mV(volts)

2.5mV(volts)

3.5mV(volts)

4.5mV(volts)

-40 -40 28.95 29.73 30.51 29.20 29.98 30.76 29.45 30.23 31.01

-35 -31 28.80 29.52 30.24 29.05 29.77 30.49 29.30 30.02 30.74

-30 -22 28.65 29.31 29.97 28.90 29.56 30.22 29.15 29.81 30.47

-25 -13 28.50 29.10 29.70 28.75 29.35 29.95 29.00 29.60 30.20

-20 -4 28.35 28.89 29.43 28.60 29.14 29.68 28.85 29.39 29.93

-15 5 28.20 28.68 29.16 28.45 28.93 29.41 28.70 29.18 29.66

-10 14 28.05 28.47 28.89 28.30 28.72 29.14 28.55 28.97 29.39

-5 23 27.90 28.26 28.62 28.15 28.51 28.87 28.40 28.76 29.12

0 32 27.75 28.05 28.35 28.00 28.30 28.60 28.25 28.55 28.85

5 41 27.60 27.84 28.08 28.60 28.09 28.33 28.10 28.34 28.58

10 50 27.45 27.63 27.81 27.70 27.88 28.06 27.95 28.13 28.31

15 59 27.30 27.42 27.54 27.55 27.67 27.79 27.80 27.92 28.04

20 68 27.15 27.21 27.27 27.40 27.46 27.52 27.65 27.71 27.7725*** 77 27 27 27 27.25 27.25 27.25 27.5 27.5 27.5

30 86 26.85 26.79 26.73 27.10 27.04 26.98 27.35 27.29 27.23

35 95 26.70 26.58 26.46 26.95 26.83 26.71 27.20 27.08 26.96

40 104 26.55 26.37 26.19 26.80 26.62 26.44 27.05 26.87 26.69

45 113 26.40 26.16 25.92 26.65 26.41 26.17 26.90 26.66 26.42

50 122 26.25 25.95 25.65 26.50 26.20 25.90 26.75 26.45 26.15

55 131 26.10 25.74 25.38 26.35 25.99 25.63 26.60 26.24 25.88

60 140 25.95 25.53 25.11 26.20 25.78 25.36 26.45 26.03 25.61

65 149 25.80 25.32 24.84 26.05 25.57 25.09 26.30 25.82 25.34


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TEMPERATURE* BFV**=54.00V BFV**=54.50V BFV**=55.00V

C F @25C(77F) @25C(77F) @25C(77F)

2.5mV

(volts)

3.5mV

(volts)

4.5mV

(volts)

2.5mV

(volts)

3.5mV

(volts)

4.5mV

(volts)

2.5mV

(volts)

3.5mV

(volts)

4.5mV

(volts)-40 -40 57.90 59.46 61.02 58.40 59.96 61.52 58.90 60.46 62.02

-35 -31 57.60 59.04 60.48 58.10 59.54 60.98 58.60 60.04 61.48

-30 -22 57.30 58.62 59.94 57.80 59.12 60.44 58.30 59.62 60.94

-25 -13 57.00 58.20 59.40 57.50 58.70 59.90 58.00 59.20 60.40

-20 -4 56.70 57.78 58.86 57.20 58.28 59.36 57.70 58.78 59.86

-15 5 56.40 57.36 58.32 56.90 57.86 58.82 57.40 58.36 59.32

-10 14 56.10 56.94 57.78 56.60 57.44 58.28 57.10 57.94 58.78

-5 23 55.80 56.52 57.24 56.30 57.02 57.74 56.80 57.52 58.24

0 32 55.50 56.10 56.70 56.00 56.60 57.20 56.50 57.10 57.70

5 41 55.20 55.68 56.16 55.70 56.18 56.66 56.20 56.68 57.16

10 50 54.90 55.26 55.62 55.40 55.76 56.12 55.90 56.26 56.62

15 59 54.60 54.84 55.08 55.10 55.34 55.58 55.60 55.84 56.08

20 68 54.30 54.42 54.54 54.80 54.92 55.04 55.30 55.42 55.54

25*** 77 54 54 54 54.5 54.5 54.5 55 55 55

30 86 53.70 53.58 53.46 54.20 54.08 53.96 54.70 54.58 54.4635 95 53.40 53.16 52.92 53.90 53.66 53.42 54.40 54.16 53.92

40 104 53.10 52.74 52.38 53.60 53.24 52.88 54.10 53.74 53.38

45 113 52.80 52.32 51.84 53.30 52.82 52.34 53.80 53.32 52.84

50 122 52.50 51.90 51.30 53.00 52.40 51.80 53.50 52.90 52.30

55 131 52.20 51.48 50.76 52.70 51.98 51.26 53.20 52.48 51.76

60 140 51.90 51.06 50.22 52.40 51.56 50.72 52.90 52.06 51.22

65 149 51.60 50.64 49.68 52.10 51.14 50.18 52.60 51.64 50.68

Table I 48 Volt Temperature Compensated Battery Float Voltage

These tables are provided as a guideline only. If battery

temperature falls between values on the above scale,

estimate the voltage setting based on the closest numericalvalues.

* Refers to ambient temperature at the battery terminal

posts.

** BFV refers to Battery Float Voltage Check battery

manufacturer's recommended settings.

*** Refers to Nominal Battery Temperature. This is the

optimum temperature for battery operation. No compensation

occurs at this temperature (use as a reference point).


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1.10 DC - DC Converter System

1.10.1 Description

ADC-DC converter system takes a DC input voltage and converts

it to the same or a different output voltage. The converter system

is utilized for any of the following reasons:

Provide different voltage levels; i.e. -48V to +24V

conversion.

Ground swapping; i.e. +24V to -24V.

Galvanic or ground isolation; i.e. +24V to +24V,

floating ground.

Voltage regulation for equipment, with a tight input

voltage operating window, operated from a batterysystem.

1.10.2 Connection

The DC-DC converter system is connected in series between the

main DC power system and the load.

A converter system consists of single or multiple parallel DC-DC

converters and may incorporate many of the features found in the

main DC power system including distribution, common ground bus

and supervisory.

DC-DC Converters should have dedicated fuse/circuit breaker

positions on the main DC power system for protection and

isolation.

If converters are located in the same relay rack as the main DC power system,

direct connection to the busswork on the input is permissible.

1.10.3 Operation

Since the converter system does not have a battery connected to its

output adjustment of the output voltage is less critical and LVDs,

temp comp, etc. are not required. The output voltage of the

converters is adjusted to match the requirements of the load and to

ensure correct load sharing between parallel converters.


56/141



1.10.4 Sizing

The converter system should be sized to adequately supply the

load under all conditions.

There should be substantial converter redundancy built in to the

converter system to account for fuse clearing and circuit breaker

tripping. If this redundancy is not built in, the converters may not

be able to clear a fault and current limiting will take effect and the

output of the converter system may be affected.

Always use fast acting fuses in converter system distribution

circuits and do not use excessively high fuse ratings.

DC - DC converter systems can add substantial load to the main

power system, allowances should be made for this when sizing themain system.


Standardization of unit for ease of maintenance.

Modularvs. monolithic configuration. Modular converters allow

for easy replacement and expansion. Supervisory and distribution

may be incorporated into a modular converter system.

High efficiency

Physical constraints in most new facilities demand compact

designs. Lightweight converters combined with space saving

designs help reduce installation and shipping costs.

Balanced load sharing should be achieved between converters.

Argus converters accomplish this with output slope regulation it is

adjustable on CS units to allow load sharing with other types of

converters. CSM units utilize a fixed slope set at 1%.

Current limiting should be provided, Argus units are factory set

at 105% of rated output, to provide protection in a overload

condition.

High voltage shutdown to switch converter off in case of high

output voltage condition, preventing damage to the load.


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Soft-start to gradually bring the converter on line from zero load

to the load requirement, eliminating high inrush currents surges.

The feeder breaker and feeder size requirements are decreased,

reducing the installation costs of the converter.

Alarms provide indication of converter failure and should be of

fail safe design. Local indication plus remote contacts are

required.


The converters are available in various input and output

configurations including 24V and 48V input; 12V, 24V and 48V

output. With current ratings from 5 Amps to 40 Amps. Specialized

converters with 130 V /100VA output are available for powering

FITL (fiber in the loop) applications.

CS series monolithic

Traditional converter packaging - each individual converter is a

stand-alone unit.

CSM series modular

Modular construction - three or four individual modules are

housed in a hardwired cabinet. Each converter is easily removed

for maintenance purposes.


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1.11 DC Power System Integration

1.11.1 Description

The DC power system integrates and connects all the components

mentioned in previous sections.

1.11.2 Connection

Intersystem

In a typical power system there should be provisions for easy

termination of intersystem cables.

Buswork should be copper; cables should meet electrical code

requirements and utilize quality compression lugs.

Lock washers or Belleville washers should be used on

electrical/mechanical connections to ensure integrity under

different temperature conditions, (high/low load). All

terminations should have provisions for connection of standard 2

hole lugs (typically 3/8 hole, 1 spacing).

Argus power systems include all these features and utilize tin-

plated copper buswork to eliminate oxidization.

The intersystem wiring and buswork determines the ultimate

capacity of the power system.

The vertical discharge riser busis used to connect the distribution

panels to the charge/discharge termination in a traditional power

system.

Battery

Separate charge/discharge configuration - This method of

connecting the battery was utilized in the past to reduce therectifier ripple voltage at the load. The vented battery was used as

a filter. With the advent of low ripple rectifiers this method of

battery termination is generally not required.


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Two busses are provided for both negative and

positive termination. Rectifier negative output cables

are terminated to one bus (- charge bus) and a cable is

run to the neg. battery terminal from this bus. A

second cable is connected from the negative batteryterminal back to the second bus (- discharge bus) and

the neg. load feed is also connected to this bus. This is

repeated for the positive side also. This method has

the added benefit of better load regulation and a

slightly reduced voltage level seen at the load.

Common charge/discharge configuration - This is the

current standard method of terminating the battery cables. One bus

is provided for the negative connections and one for the positive

connections. Rectifier output cables, battery cables and the load

feed are connected directly to these bus.

1.11.3 Sizing

Power systems should be oversized by a factor of 20-25 %. To

calculate the power system size multiple the maximum anticipated

load by a factor of 1.2 - 1.25. This over-sizing factor will ensure

that the shunt is not overloaded and that adequate capacity is

available in the buswork and cables to accommodate both the load

and battery recharge current.


Access requirements front only or front and rear.

Open relay rack or box bay.

Size restrictions.


Traditional power systems

Traditional power system packaging is in either open

relay rack or box frame. Choices of 19 and 23 rack widths.

Access is required from both the front and the rear.

Up to 10 000 amps.


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Front access power system

With less space available in many of the new

communications facilities front access power systems

have become popular. Argus front access power

systems require some rear access upon initial

installation. After initial installation the power system

may be relocated closer to the wall, with allowances

for ventilation of course.

All maintenance and circuit termination may be

performed from the front.

Up to 1200 amps.

Miscellaneous power systems

Variations on the traditional packaging techniques

include mounting the equipment in portable cabinets

on castors or utilizing wall mount brackets.

There would be obvious limitations for either of these

methods, but they do provide solutions for specific

applications and ensure flexibility of Argus

equipment.

Ultra compact power systems

RSM 48/10 and 24/18

These fully self contained power systems (except forbattery), may be configured in various packages

combining up to five rectifiers modules, distribution,

supervisory, temperature compensation and low

voltage disconnect. Packages are 17 wide, 12 deep

and 5.25 high.

RSM 48/7.5 and 24/15

These fully self contained power systems (except for

battery), may be configured in various packages

combining two or three rectifiers modules,

distribution, supervisory, temperature compensation

and low voltage disconnect. Packages are 17 wide, 12

deep and of various heights from 3.5 to 7.


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US Series

Combine battery, rectifier and supervisory in a single

package to provide either 5 Amps at 48V or 8 Amps at

24V backup time is approx. 2 hr. with internal battery.

Extra extended backup battery cabinets may be added.


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1.12 Inverters/UPS

1.12.1 Description

The inverter or Uninterruptable Power System (UPS) is utilized to

supply AC voltage to loads such as computers in the Telecom

environment. These systems are often connected to the DC power

system.

There are a various options for providing uninterruptable AC for

your loads including:

1. On-line Inverter- DC input, AC output.

Connected directly to DC main power system.

Has a standby AC line available (optional).

2. Off-line Inverter- AC input, AC output. Has a

standby DC line connection available. The DC

standby line is connected to the DC power system.

3. Double conversion UPS - Dedicated rectifier,

battery and inverter, Traditional concept.

4. Line Interactive UPS - Ferroresonant

transformer with small battery charger, battery,

inverter and intelligent control. Normal operation

is through a Ferro circuit. Ferro provides filtering

and some energy storage. Inverter is switched on-

line when required by the control. Battery charger

charges the batteries only

Type Advantages Disadvantages1 -simple -inefficient

-reliable -heavy DC system loading and inrush

-utilize main DC battery

-may be paralleled for redundancy

2 -compact

-reliable

-efficient

-utilize main DC power system

battery

3 -rugged -inefficient

-good energy storage -large, heavy

4 -compact -internal battery

-easy to install

-efficient

Table J Inverter & UPS comparison


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Both inverter system designs (type1 &2) will be discussed in this

section since they connect to and affect the operation and design

of a DC power system.

1.12.2 Connection

On-line inverter- The inverter is connected in series with the

DC power system and the connected loads. A connection is made

to a standby AC source for redundancy.

Off-line inverter- The inverter is connected in series with the

AC source and the connected loads. A connection is made to the

DC power system for redundancy.

1.12.3 Operation

On-line inverter- In normal operation the inverter draws

current from the DC power system and coverts this to AC to power

the connected load. If the inverter fails or the DC supply is

interrupted there inverter automatically transfers to a connected

AC stand-by source.

Off-line inverter- In normal operation the connected load is

powered from the AC source through the inverter. Upon loss of the

AC source the load is transferred to the inverter. There may be a

ferroresonant circuit to provide energy storage while the load is

transferred to the inverter.

1.12.4 Sizing

Inverters/UPS should be sized such that the continuous load (VA)

does not exceed 75% of the inverter rating (VA).

Inverters often supply computers that incorporate switch mode

power supplies and other non-linear loads. If loads with high crest

factors (i.e. > 2.5) are connected, the UPS rating may have to be

de-rated. See the manufacturer for further information.

Neutral current should also be monitored after UPS installation to

ensure it is within the limits of the conductor. Unbalanced loads

and low power factor often generate substantial neutral currents. It

is possible for these currents to overload the neutral conductor

since there is no protection for the neutral conductor.


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If the on-line inverter is utilized both the DC power system battery

and the rectifiers will have to be oversized to supply the additional

load imposed by the inverter.

If the off-line inverter is utilized only the DC power systembattery need be oversized since the inverter is normally operating

from the AC source and will only draw current from the DC power

system when there is a failure of the AC source.

Inverters may also draw substantial inrush current on start-up;

breaker/ fuse curve coordination may be required.


Many UPS systems combine the battery in the UPS. These

batteries rarely see proper maintenance and tend to be forgotten.These batteries never achieve proper ventilation due to the often-

cramped compartments that they occupy. Many UPS systems

utilize high DC voltage battery systems. Each of these many small

cells is the potential weak link in the chain. Powering your AC

loads from an inverter connected to the high quality, well-

maintained DC main system battery, reduces many of these

problems.


We will provide assistance in helping you chooses the right ACsolution and integrating it into the DC power system.


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CHAPTER

Power System Sizing and Ordering

2.1 Calculations2.1.1 Step 1 System load analysis

To determine your DC power system requirements evaluate your

loads and the backup period required.

Review all system components and determine:

(A) Loads that require voltage conversion.

(B) Loads that require battery backup. Dont forget AC loads i.e.

computers that require backup. Determine the individual loadcurrents for the different load voltages required. The voltage with

the highest load is generally chosen as the main system voltage.

(C) Battery details:

Main system Voltage______ current_______________

Secondary system 1 Voltage______ current_______________

Secondary system 2 Voltage______ current_______________

AC Secondary system Voltage______ Watts______ P.F.______

Redundancy N+______

Batterydischarge time hrs.______

Battery

recharge time hrs.______

Battery end Voltage______


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Warning:Check and record the polarity requirement of your connected loads.

Which polarity is connected to the common ground? This is vital information

to ensure functionality of the DC system and load.

2.1.2 Step 2 Converters

Determine the quantity and type of converters to meet each of the

secondary DC voltage requirements (if applicable).

Add redundant converters as required.

Determine the total load that the converters will have

on the main DC system. Use formula (i).

Refer to converter sizing section for extra details.

2.1.3 Step 3 Inverters

Determine the size and type of inverter to meet the secondary AC

voltage requirements (if applicable).

Determine the load that the inverter will have on the

main DC system. Use formula (ii).

Refer to inverter sizing section for extra details.

2.1.4 Step 4 Total system load

Determine the total system load using formula (iii).

2.1.5 Step 5 Total rectifier capacity

Determine total rectifier capacity. Total rectifier capacity includes

capacity to supply the load and recharge the discharged battery in

the spe

Documents

85027501 DC Power Systems Handbook