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 TM 55-1905-223-24-3
(13)
A voltage unbalance at no load indicates shorted turns in the main generator windings. Shorted
turns will destroy the insulation and can damage the main stator laminations.
(14)
Using the multimeter set to measure dc voltage, measure the voltage at the auxiliary terminal block.
Terminals 2 and 3 should be 10 to 19 volts dc. Check the dropper transformer (two transformers for
three-phase sensing) connections. Check the auxiliary terminal block conne tions. Check the three-
c
phase sensing module connections.
(15)
The no load line to line voltage range that should be obtained with 13.0 volts dc connected to exciter
leads X and XX is 305 to 335 volts.
(16)
Balanced line to line voltage within this range indicates that the generator windings and rotating
rectifiers are all in good working order. The correct voltage at the auxiliary terminal block, terminals 2
and 3, indicates that the AVR is receiving the correct no load voltage.
(17)
If the generator output voltage is not within the 305-335 volts range, check the rotating diodes. Refer to
(18)
Repeat the 13 volt no load dc excitation test. Measure the line voltage (305-335 volts).
(19)
If the generator voltage is still not within the 305-335 volt range, there probably is a defect in a rotor
winding.
(20)
After determining that all rotating diodes and the surge suppressor are good, check the rotor windings
as follows:
(a) Install the AVR by reversing step h.(l) procedures.
(b) Remove any loads connected to the generator.
(c) Open the main line circuit breaker, if equipped with one.
(d) Start the engine and bring it up to rated speed.
(21)
Adjust the line to line voltage to 240 volts.
(22)
Check the engine speed at 1797 to 1803 rpm (59.9 to 60.1 Hz). Adjust engine speed as necessary.
(23)
Measure dc voltage.
(24)
Measure and record the voltage at terminals X and XX on the auxiliary terminal block.
(25)
The voltage readings should be 5 to7 volts.
(26)
If the X to XX voltage is above 7 volts:
(a) Check to make sure the meter is set to dc voltage.
(b) Check to make sure the generator voltage is at the specified value.
4-18
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