Page 215 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

TASK 5 : Testing of transformer after winding

1 Test the primary and secondary windings for continuity with a megger.
2 Measure and record the primary and secondary winding resistance in Table 6.
Table 6
Transformer winding resistance

Primary resistance.............ohm
Secondary 1 resistance..................ohm
Secondary 2 resistance..................ohm
Secondary 3 resistance..................ohm
3 Measure and record the insulation resistance, between windings and frame in Table7.
Table 7

Insulation resistance between
Primary & secondary windings...............megohm

Secondary windings...............................megohm
(in case of seperate windings)
Windings and frame..............................megohm

4 Connect the primary winding of the transformer with the rated voltage. Keeping the secondary open, test the
primary and the secondary voltage. Record the finding in Table 8

Table 8
No-load measurement

Primary voltage........................volt
Secondary voltage
1 .............................volt
2 .............................volt

3 .............................volt

5 Observe for vibration sound of the core. If it is abnormal, tighten the stampings, also check for tightness of the
coil.
6 Connect the transformer with suiTable load so that full load current passes through the secondary, and record
the voltage and current at load in Table 9.
Table 9
Load measurement
Primary voltage..................volt
Primary current..................amp

Secondaryvoltage..............volt
Primary current..................amp

7 Keep the transformer on full load for eight hours continously. Observe the change in temperature of the
winding and core by touching. If the temperature raise is within the class of insulation, the transformer is O.K.

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CITS : Power - Electrician & Wireman - Exercise 86