8. Alternator Stand Alone

8/18/2019 8. Alternator Stand Alone

1/15

ELEN 3441 Fundamentals of Power Engineering Spring 2008

1

The Synchronous generatoroperating alone

Effects of load changes

increase in the load is anincrease in the real and!orreacti"e power drawn from the

generator#Since the field resistor is unaffected$ the field current is constant and$ therefore$ theflu%φ is constant too# Since the speed is assumed as constant$ the magnitude ofthe internal generated "oltage is constant also#

ssuming the same power factor of the load$ change in load will change the

magnitude of the armature current I A# &owe"er$ the angle will 'e the same (for aconstant PF)# *hus$ the armature reaction "oltage jX SI A will 'e larger for theincreased load# Since the magnitude of the internal generated "oltage is constant

A S A E V jX I φ = + (+#34#1)

rmature reaction "oltage "ector will ,mo"e parallel- to its initial position#


2/15


2


.ncrease load effect on generators with

Lagging PF

Leading PF

/nit PF


3/15


3


1# For lagging (inducti"e) loads$ the phase (and terminal) "oltagedecreases significantl #

2# For unit power factor (purel resisti"e) loads$ the phase (andterminal) "oltage decreases slightl #3# For leading (capaciti"e) loads$ the phase (and terminal) "oltage rises#

enerall $ when a load on a s nchronous generator is added$ the followingchanges can 'e o'ser"ed

Effects of adding loads can 'e descri'ed ' the "oltage regulation

100%nl fl

fl

V V VRV

−= (+#3 #1)

here V nl is the no5load "oltage of the generator and V fl is its full5load "oltage#


4/15


4


s nchronous generator operating at a lagging power factor has a fairl large positi"e "oltage regulation# s nchronous generator operating at a unit powerfactor has a small positi"e "oltage regulation# s nchronous generator operatingat a leading power factor often has a negati"e "oltage regulation#

Normall $ a constant terminal "oltage supplied ' a generator is desired# Since thearmature reactance cannot 'e controlled$ an o'"ious approach to ad6ust theterminal "oltage is ' controlling the internal generated "oltage E A = K φω # *hisma 'e done ' changing flu% in the machine while "ar ing the "alue of the fieldresistance R F $ which is summari7ed

1# ecreasing the field resistance increases the field current in the generator#2# n increase in the field current increases the flu% in the machine#3# n increased flu% leads to the increase in the internal generated "oltage#4# n increase in the internal generated "oltage increases the terminal "oltage of

the generator#

*herefore$ the terminal "oltage of the generator can 'e changed ' ad6usting the

field resistance#


5/15


9

The Synchronous generatoroperating alone: Example

E%ample +#2 480 :$ 0 &7$ ;5connected si%5pole s nchronous generator has aper5phase s nchronous reactance of 1#0 Ω # .ts full5load armature current is 0 at0#8 PF lagging# .ts friction and windage losses are 1#9 < and core losses are 1#0< at 0 &7 at full load# ssume that the armature resistance (and$ therefore$ the I 2 R losses) can 'e ignored# *he field current has 'een ad6usted such that the no5load

terminal "oltage is 480 :#a# hat is the speed of rotation of this generator='# hat is the terminal "oltage of the generator if

1# .t is loaded with the rated current at 0#8 PF lagging>2# .t is loaded with the rated current at 1#0 PF>

3# .t is loaded with the rated current at 0#8 PF leading#c# hat is the efficienc of this generator (ignoring the un


6/15



Since the generator is ;5connected$ its phase "oltage is

3 277T V V V φ = =

t no load$ the armature current I A @ 0 and the internal generated "oltage is E A @

2++ : and it is constant since the field current was initiall ad6usted that wa #a# *he speed of rotation of a s nchronous generator is

120 12060 1200

6m en f rpm

P = = =

which is

1200

2 125.760m rad sω π = =

'#1# For the generator at the rated current and the 0#8PF lagging$ the phasor diagram is shown# *he phase"oltage is at 0 0$ the magnitude of E A is 2++ :$


7/15ELEN 3441 Fundamentals of Power Engineering Spring 2008

+


1 60 36.87 60 53.13S A jX I j= × × ∠ − ° = ∠ °and that

*wo un



8


'#2# For the generator at the rated current andthe 1#0 PF$ the phasor diagram is shown#*hen

( ) 22 cos sin 270.4

A S A S AV E X I X I V φ θ θ = − − =

3 468.4T

V V V φ

= =and

'#3# For the generator at the rated current and the0#8 PF leading$ the phasor diagram is shown#*hen

( ) 22 cos sin 308.8

A S A S AV E X I X I V φ θ θ = − − =

3 535T

V V V φ

= =and



A


c# *he output power of the generator at 0 and 0#8 PF lagging is

3 cos 3 236.8 60 0.8 34.1out A P V I kW φ θ = = × × × =

*he mechanical input power is gi"en '

34.1 0 1.0 1.5 36.6in out elec loss core loss mech loss P P P P P kW = + + + = + + + =

*he efficienc is34.1

100 % 100% 93.2%36.6

out

in

P P

η = × = × =

d# *he input tor?ue of the generator is

36.6291.2

125.7in

appm

P N mτ

ω = = = -



10


*he induced countertor?ue of the generator is

e# *he "oltage regulation of the generator is

34.1271.3

125.7conv

appm

P N mτ

ω = = = -

Lagging PF480 410

100% 17.1%410

VR−

= × =

/nit PF

Lagging PF

480 468100% 2.6%

468VR

−= × =

480 535100% 10.3%

535VR

−= × = −



11

Terminal characteristics ofsynchronous generators

ll generators are dri"en ' a prime mo"er $ such as a steam$ gas$ water$ windtur'ines$ diesel engines$ etc# Begardless the power source$ most of prime mo"erstend to slow down with increasing the load# *his decrease in speed is usuallnonlinear 'ut go"ernor mechanisms of some t pe ma 'e included to lineari7e thisdependence#

*he speed drop (S ) of a prime mo"er is defined as

100%nl fl

fl

n nSD

n

−= ×

Cost prime mo"ers ha"e a speed drop from 2D to 4D# Cost go"ernors ha"e amechanism to ad6ust the tur'ine s no5load speed (set5point ad6ustment)#

(+#44#1)



12


t pical speed"s# power plot

Since the shaft speed is lin



13


similar relationship can 'e deri"ed for the reacti"e power Q and terminal "oltageV T # hen adding a lagging load to a s nchronous generator$ its terminal "oltagedecreases# hen adding a leading load to a s nchronous generator$ its terminal"oltage increases#

*he plot of terminal "oltage "s#

reacti"e power is not necessarillinear#

Goth the fre?uenc 5power andterminal "oltage "s# reacti"e powercharacteristics are important forparallel operations of generators#

hen a generator is operating alone suppl ing the load1#*he real and reacti"e powers are the amounts demanded ' the load#2#*he go"ernor of the prime mo"er controls the operating fre?uenc of the s stem#3#*he field current controls the terminal "oltage of the power s stem#



14

Terminal characteristics ofsynchronous generators: Example

E%ample +#3 generator with no5load fre?uencof 1#0 &7 and a slope s p of 1 C !&7 isconnected to Load 1 consuming 1 C of realpower at 0#8 PF lagging# Load 2 (that is to 'econnected to the generator) consumes a real

power of 0#8 C at 0#+0+ PF lagging#a# Find the operating fre?uenc of the s stem 'efore the switch is closed#'# Find the operating fre?uenc of the s stem after the switch is closed#c# hat action could an operator ta


15/15ELEN 3441 F d t l f P E i i

19

Terminal characteristics ofsynchronous generators: Example

a# *he fre?uenc of the s stem with one load is

161 60

1 s s nl p

P f f !"

s= − = − =

'# *he fre?uenc of the s stem with two loads is1.8

61 59.21 s s nl

p

P f f !"

s= − = − =

c# *o restore the s stem to the proper operating fre?uenc $ the operator shouldincrease the go"ernor no5load set point ' 0#8 &7$ to 1#8 &7# *his will restorethe s stem fre?uenc of 0 &7#

8. Alternator Stand Alone

Documents

Stand Alone Bulgarian

Stand Alone Flash Memories

14048352 Stand Alone Romanian

Rig Assist / Stand Alone Snubbing Unit - Mitey Titan Alone Snubbing Unit Rev.pdf · Rig Assist / Stand Alone Snubbing Unit ... • Rig Assist or Stand Alone Service is used for Low

Stand Alone DCF

stand alone risk pdf

Stand Alone Instructional Resource

Enodeb Stand Alone Project

Stand Alone project_final

Stand Alone Installation Instructions

Stand Alone Terrorism

NEVER STAND ALONE

Stand Alone Inverters

STAND-ALONE ELECTRONIC LOCKS

Stand Alone Pv Systems

Stand Alone Calibration Station

Photovoltaic Stand Alone System

Trajexia stand-alone Trajexia motion controller · PDF fileTrajexia motion controller 23 Motion controllers Trajexia stand-alone Trajexia motion controller Stand-alone advanced motion

8Channel Stand-alone DVMR

Stand Alone Presentation