Induction Generators Tharidu

8/12/2019 Induction Generators Tharidu

1/13

Calculations:

1) Self-excited Induction Generator.

Part(a): No load characteristic for varying capacitance and constant prie over speed plot

1)!ine "oltage "s #agneti$ing current

%)!ine "oltage "s &apacitance


2/13

'euired capacitance to otain rated voltage of %*+" is ,./.

110.1*

+%

%

2

1

=

=

=

=

=

=

=

rads

f

V

IC

IIHere

VCI

CiI

V

m

mc

c

c

3hen " 4 %*+ "2 f 4 + 5$

/ro the graph I4 %.% 6

7hen2 &4%.%8 (%*+1*.10)

4%0.%/

Part():No load characteristics for varying prie over speed and constant capacitance plot

1) "oltage "s Speed

%) /reuency "s Speed


3/13

) #agneti$ing current "s Speed

Part(c):Perforance of loaded generator 9ith constant speed plot.


4/13

1) "oltage "s !oad current at constant speed

%) /reuency "s !oad &urrent

) Generator &urrent "s !oad &urrent


5/13

Part(d): Perforance of the loaded generator 9ithout speed regulation plot.

1) "oltage "s !oad &urrent

%) /reuency "s !oad &urrent


6/13

) 7orue "s Speed


7/13

%) Grid connected induction generator

1) Po9er utput "s Speed

%) !ine &urrent "s Speed

) ;fficiency "s Speed

;fficiency


8/13

Input Po9er 4

;fficiency 4


9/13

6pparent Po9er 4 "I

" 4 %%*"

3atteter 'eading 4 =+3

I 4 1., 6

Po9er /actor 4,.1%%*

=+

4 +.%%

Discussion

Reason for the designing of the no-load test in a lower frequency than the rated frequency

of !"#$


10/13

Norally in induction otors2 the slip is et9een +-1(i.e. rotor speed less than

synchronous speed). >ut in induction generators slip is negative value. (i.e. rotor speed

greater than synchronous speed). Since in the no-load test 9e could not see an active po9er

output. So the slip of the generator should have a positive value or $ero(ut this is condition

of the otor). 7herefore to achieve this condition it is suitale to decrease the freuency

elo9 + 5$. 7hen 9e can have a positive slip. So that is the reason for doing the load test in

a lo9er freuency.

ause of &ariation of the &oltage and current wa&eforms of the generator loading$

3hen loading the induction otor there is slight drop in speed.

7hat is due to decrease in Nr. If 9e considering aout the induction generator the loading it

ust produce ore po9er. 7his reuires changes in Nr. 7his causes variations in voltage and

current 9avefors. Generally since induction generators cannot produce reactive po9er2

9hen reactive loads are loaded changes in voltages can e seen. Induction generators are not

self-exciting. 7hat is they reuire an external supply to produce a rotating agnetic flux. 7he

external supply can e supplied fro the electrical grid or fro the generator itself2 once it

starts producing po9er. 7he rotating agnetic flux fro the stator induces currents in the

rotor2 9hich also produces a agnetic field. If the rotor turns slo9er than the rate of the

rotating flux2 the achine acts li?e an induction otor. If the rotor is turned faster2 it acts li?e

a generator2 producing po9er at the synchronous freuency.

'mportance of induction generators oth self-ecited and grid connected in power

generation in Sri *an+a$

Induction generators are uch ore suitale for ini and icro hydro po9er

stations. #ost of the grid connected ini hydro po9er stations in Sri !an?a use Induction

generators. >ut these are not suit for high po9er applications. 7hese are also lo9 in price

copared 9ith other generators. So these generators are very econoical. 6nd also outputs ofthese generators have a very sooth voltage. 6nd these are copact in si$e.

ther advantages of induction generators can e listed as follo9s.

&heaper in cost

!ight in 9eight

&opact in si$e


11/13

Suitale for ini @ icro po9er plants.

'eliale in service

Grid connected Induction generators are suitale for 9ind po9er plants

/ree fro routine aintenance

Siple in construction

'oust in operation

haracteristics Re&ealed y the ,raphs Plotted$

$ Self Ecited 'nduction ,enerator

a$ .o *oad characteristics for &arying capacitance and constant prime mo&er speed$

i. !ine "oltage "s #agneti$ing &urrent

'ate of Increasing of #agneti$ing &urrent is increasing 9ith !ine "oltage.

ii. !ine "oltage "s &apacitance

&apacitance increases 9ith !ine "oltage.

$ .o *oad characteristic for &arying prime mo&er speed and constant capacitance$

i. "oltage "s Speed

"oltage increases 9ith the Speed nearly in a linear anner.

ii. /reuency "s Speed

/reuency increases 9ith the Speed.

iii. #agneti$ing &urrent "s Speed

#agneti$ing &urrent also increases 9ith the Speed in a linear anner.

c$ Performance of loaded generator with constant speed$

i. "oltage "s !oad &urrent

!oad &urrent Aecrease 9ith "oltage.


12/13

ii. /reuency "s !oad &urrent

/reuency reains constant after a certain value of !oad &urrent is reached.

iii. Generator &urrent "s !oad &urrent

!oad current increases 9ith generator current.

d$ Performance of the loaded generator without speed regulation$

i. "oltage "s !oad &urrent

!oad &urrent decreases 9ith "oltage.

ii. /reuency "s !oad &urrent

!oad current decreases 9ith /reuency .ut not clear enough to explain.

/$ ,rid connected 'nduction ,enerator

i. Po9er utput "s Speed

Po9er utput is increasing 9ith Speed in a linear anner.

ii. !ine &urrent "s Speed

!ine &urrent increases 9ith Speed in a linear anner.

iii. ;fficiency "s Speed

;fficiency increases 9ith increasing Speed.

iv. Po9er /actor "s SpeedPo9er /actor is also increasing 9ith Speed.


13/13

INAB&7IN G;N;'67'

N6#; : 7.7.5athurusinghe

INA;C N : ++1,;

G'BP : +

A67; / P;' : %.+0.%++0

A67; / SB> : +,.1+.%++0

Documents

Induction Generators Tharidu