* LO occurs after a provided time delay.
** Either under frequency or overcurrent cause a low voltage (LV) lockout.
Operating Condition Tabulation 500
24-21-0 Table I (Sheet 1) Feb 15/68
Page 108
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
OPERATING CONDITION OR OTHER INDICATION Refer to Paragraph 4
GCR will not close H
BTB trips without closing generator switch F1-2
Generator voltage will not build up C1-C2-E3-F5
Occurs when starting engine. GCR trips after reclosing E1
GCR trips when closing generator breaker G
One GCR and one GCB trip I
GCB will not close, BTB and GCR can be closed D1-D2-D3-D4-H
GCB will not close F8
Voltage and frequency normal with GCR closed and GCB open voltage and frequency below normal when closing GCB C1-C3-E1
BTB trips, followed by GCR and GCB, GCR will not remain closed C2-C3 E2-E3-F4-F5
BTB does not trip when closing generator switch F3-F4-F5
GCB trips following heavy load and UF condition, tripping does not occur J1
Undervoltage circuit not disabled by GCR trip circuit F6
Drive slow to prime D3-D4
Frequency varies for some time after starting engines. After running a while there are no variations D5-D6
Generator carries less load than it should E2
Frequency control potentiometer ineffective F7
500 Operating Condition Tabulation
May 01/75 Table I (Sheet 2) 24-21-0
Page 109
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
(4)
Low oil level or drive not primed.
(a) Check oil level and priming requirements. See 24-10-0, Maintenance Practices paragraph 3.F.(2).
(5)
Cold drive (low operating temperature)
(a) Operate the drive with generator not loaded for a limited period of time, until it is estimated that normal operating temperature has been reached.
(6)
Low oil pressure sensor has failed or functions improperly when cold.
(a)
Remove electrical connector from low oil pressure sensor. Check for continuity between pins 5 and 6 on pressure sensor assembly with 1000 ohm resistor in series with sensor.
(b)
Apply 115 volts 400 cycles to sensor. There should be continuity between pins 5 and 6 on pressure sensor assembly. A milliammeter should show 10 milliamperes with charge pressure applied and greater than 40 milliamperes with no pressure applied. Retain 1000 ohms in series with sensor and meter.
E. Voltage Regulator Portion of Generator Control Unit
(1)
Voltage regulator has failed internally.
(a) Check by substituting a generator control unit which contains a voltage regulator which is known to function properly.
(2)
One or more voltage sensing leads are open.
(a) With generator running check for 115 volts ac at terminals Tl, T2 and T3 to ground on voltage regulator portion of generator control unit at pins A39, A40 and A41 on the generator control unit.
(3)
Three voltage sensing leads open.
(a) Refer to step (2)(a).
F. Control, Wires and Switches
(1)
APU switch remains in contact in off position.
(a) With switch in OFF position there should not be a dc voltage at pins B10 or B25.
(2)
Defective generator switch.
(3)
Auxiliary relay has failed.
(a)
Remove electrical module P5-4 from forward overhead panel.
(b)
Replace either the auxiliary relay (K2) or (K2) or the module containing this relay.
(4)
Defective APU generator switch circuit .
(a) Check wires and switch, repair or replace.
(5)
Defective generator switch circuit.
(a) Check wires and switch, repair or replace.
(6)
Undervoltage circuit not delayed 5-9 seconds in tripping the generator control relay.
(a)
Reset the circuit and check time for low voltage annunciator light to come on.
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