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TM 10-4320-342-24
4-4. STARTER-GENERATOR REPAIR - continued.
(c)
Minimum Speed for Regulation. Operate starter-generator at 7,050 rpm, 27 volts and 200 amperes
(stabilization not required), to demonstrate ability to operate at minimum speed for regulation. Record field
current which shall not exceed 10 amperes. Calculate resistance between terminals B and Aby dividing B
to A voltage by field current. External field circuit resistance (B to A) shall be 0.4 ohms minimum.
(d)
Compounding. Operate starter-generator at 12,000 rpm and 30 volts. Apply loads of 0, 50, 100, 150 and
200 amperes. Record field current. Field current must rise with increasing load.
(e)
Commutation. Reconnect regulator and observe commutation at 30 volts, 0 amps, 100 amps and 200
amps at speeds of 7,050, 10,000 and 12,000 rpm. Record the worst condition for commutation.
Commutation must not exceed pinpoints.
CAUTION
Disconnect stator leads from terminal block and filter board leads from bearing
retainer when conducting dielectric test. Capacitors embedded in radio noise
filters will be damaged if subjected to dielectric test. A dummy terminal block may
be used for this test.
(f)
Dielectric Test. Remove starter-generator from test stand and, while still hot from testing, conduct a hi-
potential to ground test of 220 volts AC rms, 60 Hz for one minutes. Apply test voltage between each circuit
and frame. No evidence of insulation breakdown shall occur as a result of this test.
(g)
Starting Test.
CAUTION
Shunt field shall be open during starting test. Do not energize unit for more than
four seconds during test.
(1)
Rigidly mount starter-generator by its flange in a horizontal position and lock rotor.
(2)
Apply and increase voltage between terminals C and E until output torque is 13 foot-pounds. Record
terminal voltage and line current. C to E voltage shall not exceed 12 volts. Line current shall not
exceed 400 amperes.
(h)
Commutator Run-Out. Rotate armature of starter-generator on its own bearings and record commutator
total indicated run-out and the maximum bar-to-bar difference. Total indicated run-out shall not exceed
0.0008 inch. Bar-to-bar run-out shall not exceed 0.0002 inch.
4-27
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