Basics of Electricals-270213

5/20/2018 Basics of Electricals-270213

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Basic Electrical Terminology

AC Fundamentals

Voltage : V

Current : I Resistance: R

Power : KW

Energy : KWH Frequency - Hz

Power factorLead or Lag

AC / DC


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A.C.Fundamentals An alternating current (A.C.) is the current which

changes periodically both in magnitude & direction.

Voltages in a.c.system can be raised or lowered with

transformers. Raising of voltages in d.c.system is noteasy.

It is possible to build up high a.c.voltage, high speed

a.c.generators of large capacities. The construction

& cost of such generators are low. A.C.motors are simple in cosntruction & requires less

maintenance.


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Sine Waveform Mathematically it is very easy to write the

equations for purely sinusoidal waveform.

Any other type of waveform can be resolvedinto a series of sine & cosine waves offundamental & higher frequencies. Sum of allthese waves gives original waveform. Hencesinusoidal waveform is considered asstandard waveform.


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Sine Waveform The sine & cosine waves can pass

through linear circuits containing R,L & C

without distortion. Integration & derivative of sinusoidal

function is again a sinusoidal function.

This makes analysis of electrical circuitseasy.


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Sine Waveform


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Single Phase & Three Phase

System

Three Phase SystemAdvantages

The output of three phase machine is always greater

than single phase machine of same size by 1.5

times.

Occupies less space & less cost.

Less copper for transmission & distribution

Three phase motorsself starting

Gives steady output

Power factor is more compare to single phase

Economical


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Analogy to help understand

Electrical terms

Voltageis equiv. to the water pressure

Currentis equiv. to the Flow rate

Resistanceis like the pipe size

I = V/r

Pressure(V) Increases, Flow (I) Increases

Pipe Size Increases,r decreases & Flow(I)

increases.


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Voltage

Voltage: VVoltage is potential difference betweentwo points,

What it governs is the insulation thickness , materialto be used for particular line.

Different voltage used at different levels are generally

Residence voltageis 230 VAC, Industrial voltageis 415 VAC / 3.3 KV, 6.6 KV, 11KV Generation voltageis normally 11 KV

Transmission voltageis 400KV, 220 KV, 132KV Distribution voltagevaries from, 11 KV, 22 KV, 33 KV,66 KV, 110 KV, to 220 KV,


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Voltage levels

Voltage Levels For Motors:

LT Motors -- < 1000V

HT Motors -- > 1000V

Generally Available Voltages in India

LT220V,240V,415V,440VHT3.3KV,6.6KV,11KV

Generally Available Voltages Outside IndiaLT380V,660VHT3.0KV,6.0KV


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Current

Current: ICurrent flows through the line.

It governs

Conductor sizehigher conductor size to handle highcurrent

Conductor materialAluminum or copper conductors arecommonly used, copper handles more current,

Thumb rule is current density for aluminum is 0.8 A/ mm2and for copper it is 1.6 A/ mm2

Type of conductorstranded or solid.

Number of runsSingle run / double run / triple run etc

Higher the voltage lower is the current handling if powerremains constant. (Hence Transmission of Power is doneby Higher Voltage)


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Voltage and current parameters

R

Y

B

N

415VAC

415VAC

230VAC

Ir

Iy

Ib

In


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What is Power Factor?

To understand power factor, we will first start with the definition

of some basic terms:

KW is Working Power (also called Actual Power or Active

Power or Real Power). It is the power that actually powers the

equipment and performs useful work.

KVAR is Reactive Power. It is the power that magnetic

equipment (transformer, motor and relay) needs to produce the

magnetizing flux.

KVA is Apparent Power. It is the vectorial summation of KVARand KW.


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Power Factor


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Other way to define to Power Factor

Power factor: cos of phase angle difference betweenvoltage and current is called the power factor

Unity power factorWhen there is no phase angledifference between current and voltage

Lagging power factor- If current is lagging behindvoltage

Leading power factor- If current is leading beforevoltage

Unit p.f p.f. =cos (Lag) p.f. =cos (lead)VI V

V

I

I


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Power Factor

Unity power factor is better.

Inductance makes p.f. lagging, Inductancemeans any coil design

Capacitance make p.f. leading Industrial loads are normally inductive type,

hence p.f. is normally lagging-

Capacitors are used to improve p.f. These are

connected to the power system throughautomatic cut in/ cutoff circuit.


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Power

Power : Single phase P = V x I x cos

Three phase power P= 3 x VLx ILx cos

Where

P = Power consumption. VL = Line voltage IL = Line current. cos = Power factor


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Three Phase circuit

Star connection

VL

Vph

N

R

Y

B

VL =3 x V ph

IL = I ph

ILIph


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Three Phase circuit

Delta connection

VL

Vph

R

YB

VL = V ph

IL = 3 x I ph

IL

Iph


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Motor TerminalsStar connection

R Y B

U1 V1 W1

W2 U2 V2

Motor

T.B.

Supply Voltage

V2

W2 U2

V1

W1

U1

R

B

Y


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Motor TerminalsDelta connection

R Y B

U1 V1 W1

W2 U2 V2

Motor

T.B.

Supply Voltage


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Selection of cable size

Current flowing through the cable

Cable length

Cable typecopper or aluminum Voltage drop during motor running

shall be less than or equal to 3%

Voltage drop during motor startingshall be less than or equal to 10%


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MOTOR INTERLOCK LOGIC

STARTING INTERLOCK

Discharge Damper Closed (Fan Motors)

Discharge Valve Closed (Pump Motors)

RUNNING INTERLOCK

Deaerator Level Very Low(Pump I/L)

Drum Level Very low(Process I/L)


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(This circuit is made in MCC)

Phase Future Interlock

(Running interlock)

Stop PB

Start PB KM

Neutral

Motor contactor

coil

Basic circuit diagram of motor starter

Future Interlock

(Starting interlock or

Permissive)

KM


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These NO contacts

are used for interlocks

in MCC

Phase

Deaerator level

very low switch

This circuit is made in control Panel /PLC/DCS/SCADA

Neutral

Auxiliary

contactor

KA


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MOTOR INTERLOCK

MULTIPLE INTERLOCK SYSTEM

ID Fan

running

FD

Fan

run

ning

SA

Fan

run

ning

Drum

level

not

very

low

KA1

KA5

KA2

KA3

KA4

N

KA5KA3KA2KA1

P

KA4


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Case : Cable selection for 200

KW motor

Motor parameters are- 200 KW, 3ph,

339A,

Cable conductor- Aluminum Length of cable is 200 meters

Starter is option : DOL

Standard cable size chart
http://d/APRIL%202011%20PROGRAMMES/standard_cable_size.xlshttp://d/APRIL%202011%20PROGRAMMES/standard_cable_size.xls


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Motor - Selection

Following are major parameters Load GD2 Load RPM

Load MCR power consumption Test block power consumption Margin on Test block power for considering the motor

rating15% for power up to 55 KW and10% for more Standard motor rating available Look at minimumtemperature power consumption Any special accessories like VPI insulation, winding

RTD, bearing RTD, vibration sensors etc


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Motor - Selection A) DRIVEN EQUIPMENT DETAILS FOR DRIVE MOTOR SELECTION (EMS 2)

1. EQUIPMENT / APPLICATION --- FD FAN

2. MODEL --- 14144B / 1106 (TLT Engg. make)

3. METHOD OF COUPLING --- Flexible

4. RATED SPEED OF FAN --- 1480 RPM

5. GD2 AT RATED/MOTOR SPEED --- 840 kgf-m2

6. STARTING TORQUE VS. SPEED --- As enclosed

CURVE (Motor to be selected for starting with Inlet damperclosed position)

7. INSTALLATION --- Outdoor

B) DRIVE (MOTOR) DETAILS

1. MOTOR MOUNTING REQD. --- Foot (B3)

2 TYPE OF BEARINGS OF DRIVEN --- Anti friction grease lubricated

EQUIPMENT.

3. MOTOR BEARINGS --- Ball / Roller

4. DUTY CYCLE --- S1

5. SHAFT POWER AT

1) 100% MCR --- 265 kW 2) TEST BLOCK --- 334 kW @ 50 C, 374 KW @ 5 C

6. MOTOR RATING AT OPERATING --- 415 KW. CONDITION

7. CABLE SIZES FOR SIZING TERM. --- Customer to specify

BOX OF MOTORS

8. DIRECTION OF ROTATION --- Bi-directional motor

9. QUANTITY --- One

NOTE : 1) MOTOR SHALL CONFORM TO EMS1 D14-FM-CS-29480 REV. 1.

2) VENDOR SHALL SUBMIT THE MOTOR DATA SHEET & PERFORMANCE CURVES AS MENTIONED IN EMS-1.


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Motors selectionOther common

electrical parameters

Based on phases - Single phase & three phasemotors

Based on voltagesLow voltage (LT) / highvoltage (HT)

Based on working principleSquirrel cageInduction motor, Slip ring Induction motor

In Industry majority motors are Induction

motor.

Voltage, frequency, Insulation class


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MotorsImportant parameters

Enclosure /Cooling

Frame size

Duty

Fan torque speed curve

Number of starts per hour


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MOTOR PERFORMANCE

CURVES

Speed Vs Torque Curve

Thermal withstand curve

Efficiency Vs Output curve

Power factor Vs Output curve

Current Vs Starting Time / speed curve
http://d/APRIL%202011%20PROGRAMMES/motor%20curves.pdfhttp://d/APRIL%202011%20PROGRAMMES/motor%20curves.pdf


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MCC

MCC is a motor control center from

where individual loads can be controlled.

MCC takes one / two incoming powersupply and makes arrangement for

operating number of motors, heaters etc

with a different combination of rating.


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Electrical Components used in

MCC

Power contactors

Auxiliary contactors

Switch Fuse Unit

Air circuit Breaker

Current Transformer (CT)

Ammeter

Voltmeter


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Power Contactor


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Power Contactor


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Auxiliary (Control) Contactor


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2232

182512.518 42 to 450 Amps

2033 & 23 - 40

9.015, 14 - 23

6.010

4.57.5

3.05

23.3

1.42.3

0.91.5

0.61

0.450.75

0.30.50.20.33

22 - 32

1725

12.5- 18

8.5 - 12.5

5.5 - 8.5

4.06

3.55

2.4 - 3.6

1.8 - 2.7

1.4 - 2.1

1 - 1.5

0.67 - 1

45 - 75

30502033

66-110

Over Load relays


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Accessories

Accessories

Add - on auxiliary contact block 2 & 4 pole

Mechanical interlock (with top add-on provision)

Surge suppressor


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MCC contd..

INCOMER BUS-BAR OUT PUT FEEDERS CABLE CHAMBER

KW / Energy meter

MCB (MINIATURE CIRCUIT BREAKER)

Panel space heater and thermostat Control transformer


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MCC contd..

Timer

Overload relays

Push buttons Indication lamps

Selector switches ( L/R)


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MCC contd..

Component selection based on Type 2

chart.

Fuse Protected selection Fuseless protected selection
http://d/APRIL%202011%20PROGRAMMES/Fuse_Protected.dochttp://d/APRIL%202011%20PROGRAMMES/Fuseless_Protected.dochttp://d/APRIL%202011%20PROGRAMMES/Fuseless_Protected.dochttp://d/APRIL%202011%20PROGRAMMES/Fuse_Protected.doc


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MCC contd..

S.C.P.D.:Fuse / MCCB/MPCB(Isolation & Short Circuit

Protection)

Starter: contactor -Normal / overload

operations

+

Relay -Overload protectionupto locked rotor currentM

S.C.P.D.

Starter


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MCC contd..

S.C.P.D.:Fuse / MCCB/MPCB(Isolation & Short Circuit

Protection)

Starter: contactor -Normal / overload

operations

+

Relay -Overload protectionupto locked rotor currentM

S.C.P.D.

Starter


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Type 2 Selection chart

Component selection based on Type 2

chart.

Fuse Protected selection Fuseless protected selection
http://e/Train/with%20fuse%20SG%20selection%20chart.pdfhttp://e/Train/Fuseless%20SG%20selection%20chart.pdfhttp://e/Train/Fuseless%20SG%20selection%20chart.pdfhttp://e/Train/with%20fuse%20SG%20selection%20chart.pdf


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Discrimination

Contactor should carry, make and break

normal and overload currents

Relay should provide protection againstsmall overloads and single phasing.

Fuse/MCCB/MPCB should provide short

circuit protection.


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Types of Co-ordination

( IS 13947 / IEC 60947 )

TYPE 1

Damage to contactor & overload relay is acceptable.No discharge beyond the enclosure is permitted.

TYPE 2No damage to overload relay or other parts isallowed. Light welding of contacts of the contactor ispermitted if they can be easily separated (e.g. by a

screw driver) without significant deformation

Di i i ti


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Discrimination

CURRENT

TIME

CONTACTOR BREAKING

CAPACITY

Relay H.R.C. Fuse

Ico


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Type 2 Co-ordination benefits

Safe and reliable performance of products

during normal and overload conditions

Proper and proven co-ordination with shortcircuit protective device

IS / IEC / EN now make verification of co-

ordination with S.C.P.D. a mandatoryrequirement


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Design parameters which

determine MCC

Rating of MCC ( Busbar rating)

Number of incomers

Number of outgoing feeders Type of feeders DOL / RDOL/ Star Delta/

Switch fuse /ACB etc.

Draw out or non draw outAmbient temp.


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Design parameters which

determine MCC contd

Temp. rise of MCC.

Operational height

Single front or double front , IPprotection

Components of MCCMicroprocessor

based relay, heavy duty relays etc


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SYMBOLS

HRC FUSE

DOL

STARTER

STARTER

STAR/DELTA

RDOLSTARTER

VOLTMETER V


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SYMBOLS

AMMETER A

CURRENTTRANSFORMER

INDICATION LAMP

SELECTORSWITCH ss

AIRCIRCUITBREAKER/MCCB


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SYMBOLSNO CONTACT

NEUTRAL LINK

OVER LOAD RELAY

NC CONTACT

CONTACTOR COIL


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SYMBOLS

DELAY)TIMER (ON

DELAY)TIMER (OFF


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MOTOR STARTERS

DOL STARTER (Direct On Line)

STAR-DELTA STARTER

AUTO TRANSFOREMR RDOL STARTER

STATOR/ ROTOR RESISTANCE

STARTER SOFT STARTER


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ELECTRICAL DRAWING

READING

Single line diagram

sld.pdf

Power and control schematic diagram for

MCC

P _C wiring.pdf
http://d/APRIL%202011%20PROGRAMMES/sld.pdfhttp://e/Train/POWER%20&%20CONTROL.pdfhttp://e/Train/POWER%20&%20CONTROL.pdfhttp://e/Train/POWER%20&%20CONTROL.pdfhttp://d/APRIL%202011%20PROGRAMMES/sld.pdf


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ComparisionDOL and star

Delta starter

DOL Star Delta

Starting voltage Full to the motor

phases

1/3 voltage to the motorphases

Starting current Normally 6 times the

rated current

Normally 2 times the

rated current

Starting torque Normally 2.5 times of

rated torque

Normally (2.5/3) times

the rated current

Application For lower KW rating,

Our practice is for

motor rated motorthan 37 KW.

However this is not

hard and fast rule. It

is all dependant on

power supply

system

For higher KW rating,

Our practice is for

motor rated motorthan 37 KW.

However this is not

hard and fast rule. It

is all dependant on

power supply system


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Speed Torque curve

Comparison DOL and star Delta


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VARIABLE SPEED DRIVES

Conventional method of control

Needs for drives

Types of drives DC DRIVESAC DRIVES


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DC DRIVES ADVANTAGES

HIGH STARTING TORQUE

WIDE SPEED RANGE GOOD AND PREDICTABLE CONTROLSYSTEM



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DC DRIVES DIS-ADVANTAGES

Higher Maintenance

Standard DC motor not easily available Bypass arrangement is not possible incase ofDC drive failure



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AC VARIABLE FREQUENCY

DRIVE

ADVANTAGES

SOFT STARTING OF MOTOR

STANDARD AC MOTOR CAN BE USED BYPASS ARRANGEMENT POSSIBLE POWER SAVING CAN BE USED WITH PID CONTROL LOOP

FOR PROCESS CONTROL

INCREASE IN MOTOR LIFE


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AC VARIABLE FREQUENCY

DRIVE

ADVANTAGES

DIRECTION OF MOTOR CAN BE CHANGED

NO MAINTENANCE


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Things to remember while

selecting the ACVFD drive

Current Rating of motor

Ambient temperature

IP protection of ACVFD (IP 00, IP 20, IP55)

Constant torque application or Variable

torque applicationAdditional features like Communication

with DCS (Type of protocol)

Things to remember while


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g

selecting the ACVFD drive

contd.

Number of DI / DO, AI / AO

Required protections


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BATTERY

Two different metals in certain chemical

solutions can produce electricity

Metals in cell are called electrodes Chemical solution is called electrolyte

The electrolyte reacts oppositely with

two different electrodes causing oneelectrode to lose electrons & develop


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BATTERY

positive charge & other electrode to build

up surplus of electrons & develop

negative charge The difference in potential between the

two electrode charges is cell voltage


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BATTERY

TYPES OF LEAD ACID BATTERY

SEALED MAINTENANCE FREE (SMF)

SMF VRLA TUBULAR

PLANTE

NickelCadmium (Ni-Cd)


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BATTERY

Lead Acid Battery consists of two

electrodes both made of lead sulphate

(PbSO4) Electrolytedistilled water with some

sulphuric acid

Uncharged cells does not meet anyrequirements of battery

No dissimilar metals


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BATTERY

During charging, water electrolyte breaks

down & start chemical reactions.

PbSO4 changes to spongy lead (Pb),other lead sulphate changes to lead

peroxide (PbO2)

At this, good part of water becomesH2SO4 & Battery gets charged


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BATTERY

During charging,current throbatterycauses electrolysis of water & electrolyte

changes from water to mixture of water& sulphuric acid

Water molecules breaks down in two

hydrogen (H+) ions & one oxygen (O-)

ion.

(H+) & SO4(-) produces H2SO4


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BATTERY

When battery is fully charged, electrolyte

contains high percentage of sulfuric acid

as compared to water When lead acid cell supplies current,Pb

changes to PbSO4; PbO2 changes to

lead sulphate; H2SO4 changes to H2O.


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BATTERY

During discharging, both electrodes

become lead sulphate & electrolyte

contains very less sulphuric acid.


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UPS

UPS ; Uninterrupted Power Supply

Purpose : To keep the voltage constant and tomaintain the output supply voltage even if there

is no input supply voltage Parameters for designing :

Redundant or Non redundant Static bypass required or not

Battery back up time Type of batteries (Sealed maintenance free Lead Acidetc)

Voltage, KVA rating, change over time


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Rectifier & Inverter

Rectifier : Converts AC to DC Inverter: Converts DC to AC


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Earthing

Why Earthing is important

All electrical equipment shall be double earthed

GI flats, 8 SWG wire, copper or Al. cables are used for

the earthing the equipments


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EarthingRing type

Earth

Pit

Earth

Pit

Earth Mat


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Earthing

Earth

Pit

Earth

Pit

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Basics of Electricals-270213