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 TM 55-1905-223-24-3
(b) Check the exciter rotor resistance. The exciter rotor is connected to the six studs on the
rectifier assembly where the six semiconductor leads are connected (3, 5, Figure 3-6). All six
rotor leads must be disconnected and resistance measured between the forward and reverse
leads to the rotor. Refer to Table 3-2.
NOTE
A normal exciter rotor resistance reading is not distinguishable
as it is less than one ohm, but an abnormal resistance reading is
detectable.
(c) Check the main rotor resistance. The main rotor winding is connected across the two plates on
the rectifier assembly (4, Figure 3-6). Disconnect the two leads and measure he resistance
t
between the leads. Refer to Table 3-2.
(6) Check the automatic voltage regulator sensing supply from the main stator.
(a) Separately excite the generator as described in step (1) of this procedure.
(b) Ensure the output voltage is correct on the main terminals.
(c) Check the voltage on leads 2 and 3 which were disconnected and tagged from the automatic
voltage regulator in step (1) of this procedure. The voltage should be between 10 and 16 volts
dc.
(d) Remove the separately excited supply battery and connect all leads that were removed from
the voltage regulator terminals. Remove tags.
(7) Test the permanent magnet exciter. The permanent magnet exciter (4, 5, Figure 3-3) is on the non-
drive end of the generator and is isolated from all other windings. It is the main power supply to the
voltage regulator and must be tested independent of the other windings.
(a) Disconnect and tag the permanent magnet exciter leads from terminals P2, P3, and P4 onthe
automatic voltage regulator.
(b) Run the generator up to full speed.
(c) Using a multimeter, check the output voltage across leads P2, P3, and P4. The voltage
between P2 and P3, P2 and P4, and P3 and P4 should be balanced with a minimum of 150
volts at 1500 rpm (180 volts at 1800 rpm).
NOTE
The permanent magnet exciter will produce an output voltage
completely independent from the rest of the generator. It has no
effect on the separate excitation tests carried out in previous
text.
3-22
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