Page 218 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

TASK 3: Body short circuit test or ground fault test
1 Place the armature to be tested on the growler as shown in the Figure
2 Switch on AC supply is given to the growler to induced voltage in the armature winding.
3 Connected by AC milli voltmeter between the commutator segment and the shaft of the armature.
4 Observe for the deflection of the pointer of the milli voltmeter in every commutator segment.

5 Mark the commutator in which the pointer does not deflect, as it indicates contact with iron parts of the armature.

TASK 4: Drop test
1 Connect a low voltage DC supply through a variable resistance in series across the commutator segment at
distance of pole pitch. (eg. For two pole machines DC supply is given to the opposite brushes, and in four pole
machine DC supply is given to the adjacent brushes)
2 Now place the DC milli volt meter leads with the adjacent bars and find the readings for all commutator
segments as in Figure
3 Assess the windings is in good connection ff all the readings are same

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CITS : Power - Electrician & Wireman - Exercise 87