(b)
When connecting a booster battery, make certain to connect the negative battery terminals together and the positive battery terminals together.
(c)
Whenconnecting a charger to the battery, connect the charger positive lead to the battery positive terminal and the charger negative lead to the battery negative terminal.
(d)
Neveroperate the starter generator on an open circuit. Make absolutelycertain all connections in the circuit are secure.
(e)
Do not short across or ground any of the terminals on the starter generator or generator control unit.
EFFECTIVITY: PAGE 6 0 040-999
Jan10/9024-30-00
PIPERAIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
A. DCGeneration (continued)
6. Adjustmentsof Starter Generator (continued)
(f) A starter generator with reversed polarityinthe output voltagemay be corrected by flashing the field as in the procedure below:
CAUTION: DO NOT FLASH THE FIELD WHILE STARTER GENERATOR IS IN OPERATION.
(1.) Disconnect the leads to the proper generator control unit. (2.) Connect the negative terminal of a small battery (1.5 to 6 volts), or an equivalent dc power supply, to terminal E of affected starter generator. (3.) Connect a jumper wire from positive terminal of same battery to terminal A of same starter generator.
NOTE: If flashing the field fails to correct generator polarity, check for incorrect connections or defective field circuit.
7. Starter Generator Service Test Specifications
Lear Siegler leading particulars for the 28-volt starter generatorsinstalled as standard equipment are as follows: CHART 2 STARTERGENERATORTESTSPECIFICATIONS
Rating (Minimum Continuous)
175amperes, 28 volts at ground idle speed of 6,720 rpm.
300amperes, 28 volts at 6,950 rpm.
300amperes, 30.0 volts to maximum rated speed of 12,000 rpm.
External Starting Power Limitations: 1,700 amperes maximum,self-limitingwith 30 volts maximum at start receptacleand 0.004 ohm aircraft circuit resistance when power supply is connected to terminal B (shunt start).
Cooling...... .................................... CombinationSelf-Cooled& Blast Air
3.00inches
Air Inlet Opening Diameter .......................................................................................................
00 inches
OverallLength (Less Spline Drive) ........................................................................................
Housing Diameter ............................................................................................................... 86 inches
Weight(Including QAD Kit)* (Approx)................................................................................... 55 pounds
inch-pounds
OverhungMoment (Approx).............................................................................................153
Counterclockwise
Directionof Rotation (Viewing Drive End) ......................................................................
DriveSpline & Mounting Flange............................................................................... MS3331-1P
Numberof Teeth in Drive Spline.............................................. ....
DriveSpline Pitch Diameter............................................... ... .... 0.600 inch
DriveShaft Shear Torque (Nom.)................................................................. 1,600inch-pounds
Terminal Designations
Positive....................................................................................B+
Negative........................................................................................ E-
PositiveField..................................................................... A+
Equalizer........................................................ ........... ..D
EFFECTIVITY:
040-999
PAGE
24-30-00 Jan 10/90
PIPERAIRCRAFT
PA-42-720 (Advanced Trainer)
MAINTENANCEMANUAL
A. DCGeneration(continued)
8. CheckingStarter Generator System
Thestartergenerator system incorporatestwo ammeters which provide an independent output
checkof each generatorand a voltmeter which monitorsthe electricalbus voltage. Should either
ammeterfailto indicate an output from its associated generator,checkthe appropriate circuit
breaker(referto 24-61-02 wiring diagram manual). If the circuit breakersare in their normal
operatingposition,a further check of the system shouldbe accomplished.
(a)
Ensure that the ammeters areoperatingproperly.
(b)
Ensure that all electrical units are off and battery is fully charged.
(c)
Disconnectelectricallead at terminal stud B+ on starter generator being tested (L or R).
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