Sizing and Installing CUMMINS

8/12/2019 Sizing and Installing CUMMINS

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L o a d Co n s id e r a t i o n s 1

Generator Set Load Considerations& Recommended Installation

Presented by Sean Manzof Cummins Western Canada




Sizing GenSets

• P r o p e r l y s i z i n g a g e n s e t f o r a g i v e n a p p l i c a t i o n

c a n b e a d i f f i c u l t t a s k .

• Th e p u r p o s e o f t h i s p r e s e n t a t i o n i s t o i n f o r m

i n d i v i d u a l s w h o d e s i g n p o w e r g e n e r a t i o ne q u i p m e n t i n t o t h e i r p r o j e c t s .

• A l t h o u g h q u i t e t h o r o u g h , t h i s p r e s e n t a t i o n

d o e s n o t c o n t a i n a l l o f t h e i n f o r m a t i o n , co d e s ,

a n d d e s i g n g u i d e l i n e s r e q u i r e d b y t h ea u t h o r i t i e s h a v i n g j u r i sd i c t i o n .




Sizing GenSets

• Th e r e a r e s e v e n m a i n q u e s t i o n s a d e s ig n e r n e e d s

t o a n sw e r w h e n p r o p e r l y s i z i n g a g e n s e t f o r a n y

a p p l i ca t i o n . Th e se q u e s t i o n s i n c lu d e :

– What is the nature of the load that is to be supplied?

– What are the performance expectations of the powersupply?

– What are the physical size constraints?

– What does the budget allow for?

– What fuel is available (by code?) for the powersupply?

– What is the life expectancy of the power supply?

And most importantly,

– What is the power supply expected toaccomplish?




Nature of the load

• I t i s v e r y im p o r t a n t t o d e t e r m i n e w h a t k i n d o f

l o a d i s g o i n g t o b e o p e r a t e d f r o m a g e n s e t .

– I.E. 100kW of resistive load vs. 100kW of inductive

(motor) load vs. 100kW of non linear (SCR) load willrequire three different gensets

• H o w i s ( a r e ) t h e l o a d ( s ) o p e r a t e d ?

– I.E. What kind of motor starters are used? What are

the motors operating? When do the loads operate?• W h a t p o w e r su p p l y t o l e r a n c es is ( a r e ) t h e l o a d ( s )

a b l e t o o p e r a t e o n ?

• U n l i k e a u t i l i t y p o w e r s u p p l y w h i ch h a s r e la t i v e l y

s t e a d y f r e q u e n c y a n d a v a r y i n g v o l t a g e , a g e n s e t

h a s a r e l a t i v e l y s t e a d y v o l t a g e a n d a v a r y i n g

f r e q u e n c y .




Performance

• U n l i k e a u t i l i t y p o w e r su p p l y ( i n m o s t c a s e s ) a

g e n se t i s a L I M I TED p o w e r su p p l y .

• A p r o p e r l y s i z e d g e n s e t w i l l p o w e r t h e l o a d s

w i t h i n t h e i r d e s i g n p a r a m e t e r s , f o r e x a m p l e :

– A typical magnetic motor starter contactor will stayenergized during a 25% undervoltage condition.

• I d e a l l y t h e d e s i g n e r n e ed s t o d e t e r m i n e w h a t a r e

t h e m a x im u m v o l t a g e a n d f r e q u e n c y d i p

t o l e r a n c e s t h a t t h e l o a d s w i l l a c ce p t .




Physical Size

• H ow m u ch s p a ce i s a v a i l a b l e t o i n s t a l l t h e

r e q u i r e d e q u i p m e n t ?

• Co n s i d e r a l l i t e m s p o t e n t i a l l y r e q u i r e d i n c l u d i n g :

– Genset

– Transfer switch

– Battery charger– Batteries

– Exhaust system

– Fuel storage

• I n s o m e l a r g e l o a d s i t u a t i o n s i t m a y b e n e ce ss a r y

t o h a v e t w o u n i t s o p e r a t i n g i n p a r a l l e l .




Budget

• A n o b v i o u s co n s t r a i n t .

• Th e b e s t s o l u t i o n t o b u d g e t s i t u a t i o n s i s t o t a l k t oy o u r l o ca l p o w e r s y s t em s r e p r e s e n t a t i v e .




Fuel supply

• W h a t f u e l su p p l y i s a v a i l a b l e ?

• W h a t f u e l s u p p l y i s r e l ia b l e ? • W h a t f u e l su p p l y i s co s t e f f e c t i v e ?




Life expectancy

• I m p o r t a n t f o r p r im e p o w e r a p p l i c a t i o n s .

• H o w m a n y r e b u i l d s w i l l b e r e q u i r e d d u r i n g t h el i f e o f t h e p r o j e c t ?

• D o e s t h e d e s i g n e d l i f e e x p e c t a n c y o f t h e

p r o j e c t c o v e r t h e p o s s i b i l i t i e s o f o b so l e sc e n ce ?



L o a d Co n s id e r a t i o n s 1 0

What is expected

• W h a t i s t h e g en s e t e x p e c t e d t o d o ?

• Ta k e a m o m e n t t o s t o p a n d t h i n k a b o u t y o u r

r e q u i r e m e n t s s i n c e i t i s v e r y e a sy t o c o n f u s ey o u r s e l f w i t h f e a t u r e s t h a t y o u c an p r o b a b l y

d o w i t h o u t .

• W h o a r e t h e s t a k e h o l d e r s i n y o u r d e s i g n ?

– Client / end user– Maintenance personnel

– Code authority / Fire Marshall




Site conditions

• E l e v a t i o n

• Tem p e r a t u r e

• H u m i d i t y

• A t m o sp h e r i c c o n t a m i n a t e :

– Dust

– Corrosive gasses

– Pollen




Ratings

• St a n d b y r a t i n g - A p p l i c a b l e f o r s u p p l y i n g

e m e r g e n cy p o w e r f o r t h e d u r a t i o n o f a n o r m a l

p o w e r f a i l u r e . Th e r e i s NO SUSTA I N EDOVERLOAD c a p a b i l i t y a v a i l a b l e a t t h i s r a t i n g .

• P r im e r a t i n g - A p p l i c a b l e f o r su p p l y i n g p o w e r in

l i e u o f c o m m e r c i a l l y p u r c h a s e d p o w e r . P r im e

p o w e r i s t h e m a x im u m p o w e r a v a i l a b le a t a

v a r i a b l e l o a d f o r a n u n l im i t e d n u m b e r o f h o u r s . A

1 0 % o v e r l o a d c ap a b i l i t y i s a v a i l a b l e f o r a l im i t e d

t im e ( 1 h o u r i n 1 2 h o u r s )

• Co n t i n u o u s r a t i n g - A p p l i c a b l e f o r su p p l y i n g

p o w e r c o n t i n u o u s l y t o a l o a d f o r t h i s r a t i n g . Th e

co n t i n u o u s l o a d r a t i n g d o e s n o t c h a n g e .




Load Considerations




Common Loads

• L i n e a r

• N o n - l i n e a r

• L i g h t i n g

• H e a t i n g

• U PS / B a t t e r y c h a r g i n g

• A i r c o n d i t i o n i n g

• El e c t r i c m o t o r s f o r :

– pumps

– conveyors

– fans / HVAC

– artificial lift

– elevators




Linear LoadVoltage

In-phase Current

Leading Current

Lagging Current

• Current Proportional

to Supply Voltage

• Current in or Out of

Phase With Voltage

• Incandescent Light

and Heating Loads




Nonlinear LoadVoltage

Non Linear Current

• Current Disproportional

to Supply Voltage

• Current in or Out of

Phase With Voltage

• UPS, VFD, Battery

chargers, etc




Nonlinear Loads

• Load Induced Harmonic Currents(THDI) Cause:

– I n c r e a se d L o s se s an d H e a t i n g

– So u r c e V o l t a g e D i s t o r t i o n ( TH D V )

– O b j e c t i o n a b l e N e u t r a l Cu r r e n t s

– L o ss o f Ge n e r a t o r V o l t a g e Co n t r o l ( SCRT r a c k i n g )

• Generator Voltage Distortion (THDV)

– Po s s i b l e Co n t r o l I n t e r a c t i o n : Sy s t e mI n s t a b i l i t y

– No t c h i n g D i s a b l e s UPS B y p a s s

– H a r m f u l t o Co n n e c t e d Lo a d s




Overcoming Nonlinear Loads

• Oversized Alternators Recommended

– M i n i m i z e Ge n e r a t o r V o l t a g e D i s t o r t i o n

– Com p e n s a t e f o r H e a t i n g

• Load Harmonic Filters (properly sized)

– Le a d i n g PF o n L i g h t l y Lo a d e d U PS

– Lo s s o f Ge n e r a t o r V o l t a g e Co n t r o l

( Ca p a c i t i v e V a r s M a i n t a i n Ex c i t a t i o n )




Lighting

• Lighting loads are fairly straightforward tocalculate

• Typical formula is:

– total load (kW) = lamp wattage + ballast wattage

• Of course the power factor of the light should alsobe taken into consideration

H i




Heating

• Heating loads are also quite simple to calculate

• Electric heaters are typically resistive loads and

run at unity power factor

• Keep in mind that some heaters have circulatingfans that would need to be added to thecalculation

UPS / B tt Ch




UPS / Battery Charger

• Static UPS systems use SCR’s to convert AC to DCto charge the batteries

• Inverters change this DC voltage back to AC at theoutput

• These switching (firing) SCR’s induce harmoniccurrents in alternators which cause waveform

distortion, winding heating, and reducedefficiency

• Larger alternators combat this problem as they

can absorb higher harmonic elements• UPS’s are sensitive to voltage and frequency

fluctuations on the input especially when thebypass is enabled

UPS / B tt Ch





• Past compatibility problems between gensets andUPS were common

• UPS suppliers recommended oversizing gensets 2-5 times in the past

• UPS suppliers have addressed compatibilityproblems and have developed cleaner conversion

systems

• Typically now, to save costs, indicate to thesupplier that the UPS may be powered from a

genset instead of grossly oversizing the genset.

UPS / B tt Ch





• For sizing purposes take the UPS full nameplaterating plus the battery charge rating

• Some UPS have a current limit setting whichwould be the total current required to supplypower to loads and the battery

• These are “non-linear” loads

• Harmonic filters may be used to reduce theharmonics on the line. Beware when using filterson a lightly loaded UPS as these filters, typically

capacitive filters, may cause a leading PF on thegenset output.

Air Conditioning




Air Conditioning

• Typically sized in tons

• Rule of thumb is 2 h.p. per ton. This is

conservative for a lower efficiency unit• More exacting load calculations would require the

summation of all motors and heaters as part ofthe unit including remote cooling towers.

Motor Loads




Motor Loads

• Low and high inertia loads is determined by themoment of inertia of a rotating mass or a measure

of resistance to acceleration by motor startingtorque

• Rule of thumb - low inertia loads can beaccelerated by a motor when the calculated

service factor is 1.5 or less. High inertialoads…….service factor >1.5

• Low inertia = fans, centrifugal blowers, rotarycompressors, rotary and centrifugal pumps

• High inertia = elevators, loaded conveyors,cylinder pumps and compressors, rock crushers

Typical Motor Characteristics




Typical Motor Characteristics

• High PeakStarting Current

• Low StartingPower Factor

• High Peak kWDuringAcceleration

• TorqueProportional toSquare of Voltage

P E R C E N T T O R Q U E , P O W E R , C

U R R E N T

PERCENT MOTOR RATED SPEED

20 40 60 80 100

100 0.2

1.0

P O W E R

F A C T O R ( L A G G

I N G )

600

Motor Current

Motor Power Factor

Load Torque

Motor Torque



Motor Starting Methods





• Variable Frequency Drives (VFD’s)– Classified as non linear load

– Induces harmonics

– Size for the drive, not the motor– Oversized alternator required for:

• overheating caused by harmonics

• reduced THDV resulting from lower alternatorreactance

– Conventional VFD’s:

• Rule of thumb = oversize alternator 100%– VFD w/ PWM:

• Lower harmonics

• Rule of thumb = oversize alternator ˜40%






• Soft Starts - Solid State– “trade name”

– Classified as non linear

– SCR firing– Frequency specific as frequency dictates

SCR firing timing

– Current limit

– Auto bypass

– ASK THE MANUFACTURER ABOUTPOWERING THE STARTER FROM AGENSET!!!






• Part winding, auto transformer, capstart - run, etc:

– Motor starting torque

General Motor Starting Considerations




General Motor Starting Considerations

• Rule of Thumb: 1/2 HP per kW

• Rule of Thumb: Start What Will Run (If DipAcceptable)

• Apply Reduced Voltage or Soft Start Only toLow Inertia Loads

• Watch Out for Transition on Reduced Voltage

Starters• Start Large Motor Loads First

• S p e c i f y :

– M in i m u m o f 9 0 % Su s t a i n e d Vo l t a g e f o r

A cc e p t a b l e M o t o r T o r q u e

– PMG f o r L a r g e M o t o r Lo a d s an d So l i d St a t e

S t a r t e r s

• Watch Cyclic Loads

Generator Set Characteristics




Generator Set Characteristics

• Limited Power Source– Lo a d Ch a n g e Y i e l d s V o l t a g e a n d

Fr e q u e n c y D i s t u r b a n c e

– En g i n e k W

– A l t e r n a t o r k V A

• Several Alternator Sizes Available

– Tem p e r a t u r e R i s e

– Ex t e n d e d Ra n g e

– Fu l l S i n g l e Ph a s e Ou t p u t • Excitation Systems

– Se l f Ex c i t e d

– Se p a r a t e l y Ex c i t e d

Self Excited (Shunt) Generator




Self Excited (Shunt) Generator

Main Stator

Regulator Reference

Exciter

Field

Sensing

Power

Main Field

Rotating

Diodes

Power

Input

Exciter

Rotor

Separately Excited (PMG) Generator




Separately Excited (PMG) Generator

Main Field

Main Stator

Regulator Reference

Exciter

Field

Exciter

Rotor

Rotating

Diodes

Sensing

Power

Power

Input

PMG

Stator

PMG

Rotor

Generator Set Comparison




Generator Set Comparison

SeparatelyExcitedSelf Excited

• Lower Voltage Dips

• Sustained Fault

• Three Phase RMSSensing

• Voltage Centering

• Non-linear LoadImmunity

• Excellent MotorStarter

• Higher Voltage Dips

• Collapsing Field

• Single PhaseAverage Sensing

• Voltage Unbalance

• Lower Tolerance forNon-linear Loads

• Good Motor Starter

Conclusions and Recommendations




Conclusions and Recommendations

• Try Stepping Loads to Optimize Generator Set Size

– Re q u i r e s M u l t i p l e Tr a n s f e r Sw i t c h e s o r O t h e r L o a d Co n t r o l

– St a b i l i z e Ge n e r a t o r B e t w e e n St e p s

• Start Large Motors and Life Safety Loads First

• Whenever Non-linear Load Content Exceeds 15%,Specify PMG and Isochronous Governing (Always WithUPS)

• Consider Impact of Cyclic or Other High Surge Loads

• Avoid Leading Power Factor

• Apply Reasonable Limits on Generator TransientPerformance and Allowable Frequency Slew Rate

• Analyze Load Unbalance When 3 Phase UPS SuppliesSingle Phase Load (Single Phase Bypass)




Genset Installations




• Th e f o l lo w i n g p r e se n t a t i o n w i l l d i s c u s s a ss o c i a t e di t e m s a n d c r i t e r i a f o r p r o p e r l y d e s i g n i n g a n d

i n s t a l l i n g g e n s e t s

• Th i s p r e s e n t a t i o n w i l l co v e r b o t h e l e c t r i c a l an d

m e ch a n i ca l co n s i d e r a t i o n s

• W h i le t h e r e a r e m a n y d i f f e r e n t m e t h o d s o fi n s t a l l i n g g e n e r a t i o n e q u i p m e n t , t h i s p r e se n t a t i o n

i s f o r t h e p u r p o s e o f i n f o r m i n g o n l y . I t i s n o t t o

b e u s e d s p e c i f i ca l l y f o r d e s ig n a p p l i ca t i o n s .

• Th i s i n f o r m a t i o n i s t a k e n f r o m t h e Cu m m i n s T- 0 3 0

m a n u a l f o u n d o n o u r l i t e r a t u r e CD .

Preliminary Design




y g

• Why is a back up generator set required?

– Emergency loads, critical load support, life safety loads• It is important to determine what the loads do. This will

determine any specific codes that you need to follow,including but not limited to:

– CSA C282-00 - Emergency Electrical Power Supply forBuildings

– CSA Z32-99 - Electrical Safety and Essential ElectricalSystems in Health Care Facilities

– Canadian Electrical Code

Sizing




g

• Now that you know what purpose the genset is to serve,

you will need to size the genset properly.

• For the purpose of this presentation, it is assumed thatthe “Sizing gensets” presentation has already been

completed or that the class is already aware of thecommon practices in sizing gensets.

Fuel Supply




pp y

• So we know what our genset will do and what size is

required, we still need to know what kind of fuel it willburn.

• Again, the type fuel used by the genset may be dictatedby the codes having authority.

• You typically can’t go wrong with choosing a dieselgenset with respect to code regulations and purchasecost.

Location




• Where are we going to put this thing?

– Outside or inside?– Existing structure(s)

– Location of loads, distribution panels, service entrance

– Availability/location of genset support power

– Security from flooding, fire, vandalism, weather– Contamination of environment

– Possible simultaneous damage to normal and emergencyservice

– Service accessibility for both minor and major repairs &routine maintenance (including 100% load tests)

Outdoor Location Considerations




• Airborne noise and noise treatment

• Skin tight, drop over or walk in enclosure• Proximity of enclosure to other structures with

maintenance and repairs in mind

• Security fences and sight barriers

• Property line distances and available property

• PREVAILING WIND

• Grounding locations

• Architectural• Fuel location

Indoor Location Considerations




• Airborne noise and noise treatment • Code issues - devoted room, fire walls• Accessibility of equipment with maintenance, testing

and repairs in mind • Ventilation and ventilation effects on other equipment • PREVAILING WIND

• Above grade structure capabilities• Grounding locations• Provisions for artificial load connection• Fuel location and storage

Fuel Storage Considerations




• Capacity of tank

– Can be driven by Codes and local authorities– Consider fuel turnover when testing genset

• Environmental concerns

• Location of tank

– Filling

– Proximity to genset

– Day tank and transfer pumps may be required

• LPG storage - consult local authority

Noise Considerations




• City bylaws and local authorities

• Location of inlets and discharge louvers• Directional hoods

• Block walls and or trees/shrubs

• Specific acoustical materials

• Low flow radiators or water to water heat exchangers

Emissions Considerations




• ????? Kyoto ?????

• Company guidelines• EPA requirements

• Emissions credits

• Exhaust catalysts and aftertreatments

Wind Considerations




• The prevailing wind of the location is quite important to

know as two very serious problems can arise if the wingdirection is not taken into consideration:

– The wind may blow the engine exhaust to unfortunate

locations such as building fresh air inlets, residential areasor busy roads

– The radiator air flow may be restricted if significant wind is

blown directly into the engine radiator discharge

Weather Considerations




• More specific for outdoor gensets, weather plays an

important role in installation design– Snow/wind loads on buildings and enclosures

– Snow/leaf drifting by inlets or clogging outlets

– Cold/hot ambient temperatures

– Critters and insects– Airborne particulate, dust, pollen, etc.

– Humidity

• Some of these items will determine the genset accessories required.







Questions?




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Sizing and Installing CUMMINS