Turn Ratio and Polarity Test on a Single Phase Transformer

INTERNATIONAL ISLAMIC UNIVERSITY, ISLAMABAD

Faculty of Engineering and Technology

Department of Electrical Engineering




LABORATORY MANUAL

ELECTRICAL MACHINES - I

LAB No 02: Turn Ratio and Polarity Test on a Single Phase Transformer

GROUP A

NAME REGISTRATION NO

HASSAN ALI 66-FET/BSCEET/F20

ABOUBAKAR BIN MUSHTAQ 67-FET/BSCEET/F20

MUHAMMAD AMMAR 63-FET/BSCEET/F20

ABDULLAH HAFEEZ 64-FET/BSCEET/F20




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, LAB NO:02

Turn Ratio and Polarity Test on a Single Phase Transformer

 Objective:
The performance of a transformer largely depends upon perfection of turn ratio. So
transformer turn ratio test is an important test of transformer.

Polarity test is needed for identifying the primary and secondary side polarities. Polarities of
windings must be known if transformers are connected in parallel to share a common load.

For three-phase connection of transformers, the winding polarities must also be known.

 Required Equipment:
1. Variable single phase AC supply
2. Voltmeters
3. Single phase transformer
 Theory:
It is essential to know the relative polarity at any instant of primary and secondary terminals
for making correct connections. When the two transformers are to be connected in parallel
to share the load on the system.

The marking is correct if voltage V3 is less than V1, such a polarity is termed as subtractive
polarity. The standard practice is to have subtractive polarity because it reduces the voltage
stress between adjacent loads. In case V3 > V1, the EMF induced in primary and secondary
have additive relation and transformer is said to have additive polarity.

1. Turn Ratio Test:




Figure 1: Circuit Diagram Of Turn Ratio Test




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