PARALLEL OPERATION OF ATWO SINGLE PHASE TRANSFORMER
OBJECT : To find the load shared by two single phase transformer of equal capacity.
APPARATUS:
Sr No. Item No. reqd. Range Remarks
1. Transformer
2. Ammeter
3. Ammeter
4. Voltmeter
5. Voltmeter
6. Load Resistance
THEORY:
In order to connect two single phase transformer in parallel the following condition must be full filled.
1. The palralies must be same if this is not done. It will in a dead short
circuited.
2. The voltage ratio must be same. This is necessary to avoid the no load circulating current. The impedance of the transformer is very small and hence the circulating current is very high causing additional copper loss when the transformer are loaded. This circulating current tends to produce un equal loading conditions resulting in to one of the transformer getting exessively hot.
3. They must have equal % impedance and equal capacities otherwise the load shared by transformer with unequal capacities will be propotional to their rating.
The share by two transformer can be determined from the formula.
QA = QZB . & QB = QZA .
ZA + ZB ZA + ZB
Where QA & ZA are the load shared and impedance of first transformer, QB & ZB the corresponding values for the second & Q the total load to be shared.
4. KVA rating of transformer must be same, if the rating is not same the transformer which is having low rating will be over loaded.
PROCEDURE :
1. Connect the transformer in parallel after testing the polarities.
2. Vary the load current & note the load current shared by two transformers by ammeters.
OBSERVATION TABLE :
Sr No. Voltage in volts V Total current in amp IT Load current in amp I1 Load current in amp I2
1.
2.
3.
4.
5.
6.
7.
CALCULATIONS:
CONCLUSION: