Page 116 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

TASK 3 : Connect and verify the voltage of 3 Ph. Auto transformer
1 Connect the primary input terminals (R S T) of 3 Ph. Auto transformer to 3 ph. Mains, and set its knob to zero
position.
2 Connect the voltmeter across secondary output terminals (U V W)
3 Switch ON the main supply and measure the primary input line voltage & record.
4 Slowly rotate the knob clockwise and measure the variable 3 Phase output voltage across secondary terminals.

5 Increase the voltage step by step and record the output voltage until last taping of winding.
6 Reduce the voltage to zero and switch OFF the supply & disconnect the auto transformer.
Tabular column:

Primary Input Voltage Tapping No. Secondary Output Voltage (V )
(V ) S
P
1 Ph. Auto Transformer 1 Ph. 230 V 1

2
3

4

3 Ph. Auto Transformer 3 Ph. 415 V 1
2

3

4

Safety precautions:
1 Handle the auto transformer carefully as it is heavy.
2 Select higher range in voltmeter while measuring 3 Ph. voltage
3 Set knob to zero position before switching ON the auto transformer.
4 Ensure the earthing for auto transformers.

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CITS : Power - Electrician & Wireman - Exercise 48