Specifications

Adjust the readings to a specified value, by using a variable rheostat. Record the milli-

voltmeter readings on the consequent commutator segments by rotating by rotating the armature

in one direction. The position of the segments and the connection should be the same as in the

first set up. The result could be concluded as enumerated below.

1) If all the readings are the same, the winding is correct.

2) If the millimeter reads zero or low voltage, the coil connected to the segment is short.

3) If the milli-voltmeter reads high voltage, the coil connected to the segments is open.

4) If the milli-voltmeter deflects in the reverse direction as shown in fig, the coil connected

with the segments is reversed.

Generally armatures are tested as a routine for insulation resistance and for shorted coils.

Only when a fault in the armature winding is suspected, a drop test is conducted.

Fig. 6.21