No attempt should be made to unbolt and
separate the parts of the rotor. Breaking the
magnetic circuit would alter the permanent
Reassembling the rotor would not restore
the magnetism to its prior state.
ROTATING RECTIFIER. The rotating rectifier
assembly is part of the exciter rotor. (See figure 11-13.)
The rotating rectifier assembly consists of a full wave
rectifier bridge made up of six semiconductor devices
mounted on aluminum heat sinks. Rectifiers are retained
in the heat sink assemblies with retaining nuts and
Inspection. Check wiring for loose
connections and diodes for looseness in
Test. Remove cover (20, figure 11-3) to
gain access to the rotating rectifier
assembly on exciter rotor (38).
Disconnect lead from diode under
Refer to figure 11-14, then
connect ohmmeter leads across rectifier in
one direction. Note meter reading.
Reverse leads and note meter
reading. The meter should indicate a low
resistance when leads are across rectifier in
one direction and a high resistance when
leads are across rectifier in the other
If the meter indicates a low resistance in
both directions, the rectifier is shorted. A
high resistance in both directions indicates
an open rectifier.
Check resistance of surge protector
(varistor) when disconnected from one side
of generator field. Value should be 1
megohm or more in each direction. Check
to be sure no physical damage is evident
on the surge protector.
Removal. Remove the rotating rectifier
assembly as follows:
Remove cover (30, figure 11-3) by
removing screws (26 and 28),
washers (29), and nuts (27).
Disconnect leads from (+) and (-)
terminals located on the heat sinks
of the rotating rectifier assembly.
Figure 11-13. Rotating Rectifier Assembly