CAC / BDP 7 kW NG Diagnostic Repair Manual
Also see for FOR BYPASS AND FAN POWERED HUMIDIFIERS: Owner's manualOwner's manualOwner's manual
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Contents
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teSt 18 – check VoltaGe andFrequency under loadDISCUSSION:It is possible for the generator AC output frequencyand voltage to be good at no-load, but they may dropexcessively when electrical loads are applied. Thiscondition, in which voltage and frequency drop exces-sively when loads are applied, can be caused by (a)overloading the generator, (b) loss of engine power, or(c) a shorted condition in the stator windings or in oneor more connected loads.PROCEDURE:1. Connect an accurate AC frequency meter and an ACvoltmeter across the stator AC power winding leads.2. Start the engine, let it stabilize and warm-up.3. Apply electrical loads to the generator equal to the ratedcapacity of the unit.4. Check the AC frequency and voltage.a. Single Cylinder Units: Frequency should notdrop below approximately 58 Hertz. Voltageshould not drop below about 230 volts.b. V-Twin Engine Units: Frequency should not dropbelow approximately 60 Hertz. Voltage shouldnot drop below about 240 volts.RESULTS:1. If frequency and voltage drop excessively under load,refer back to flow chart.2. If frequency and voltage under load are good, dis-continue tests.teSt 19 – check For oVerloadconditionDISCUSSION:An “overload” condition is one in which the generatorrated wattage/amperage capacity has been exceed-ed. To test for an overload condition on an installedunit, the best method is to use an ammeter. See“Measuring Current” in Section 1.5.PROCEDURE:Use a clamp-on ammeter to measure load current draw, withthe generator running and all normal electrical loads turned on.RESULTS:1. If the unit is overloaded, reduce loads to the unit’s ratedcapacity.2. If unit is not overloaded, but rpm and frequency dropexcessively when loads are applied, go to Test 16.teSt 20 – check enGine conditionDISCUSSION:If engine speed and frequency drop excessivelyunder load, the engine may be under-powered. Anunder-powered engine can be the result of a dirty aircleaner, loss of engine compression, faulty fuel set-tings, incorrect ignition timing, etc.PROCEDURE:For engine testing, troubleshooting and repairprocedures refer to Problem 11 in Section 4.3.For further engine repair information refer to theappropriate engine service manuals.teSt 21 – Field FlaSh alternator(8-10 kW unitS)DISCUSSION:The alternator utilizes residual magnetism within thewindings to charge the capacitor. If the generator hasbeen sitting for a long period of time with no activitythe residual magnetism could be lost within the rotor.Field flashing the rotor while connected in parallel withthe capacitor will force a charge of electricity throughthe DPE winding. The voltage that is induced into therotor will return and charge the capacitor enough totake over voltage regulation of the unit.note: it is crucial that the generator exercise oncea week to help maintain this residual magnetism.*Warning: Please keep safety in mind whileperforming this test.PROCEDURE:1. Construct an energizing cord that is similar to that shownin Figure 17 and connect it as shown in Figure 18.2. Set the AUTO-OFF-MANUAL switch to the OFF position.*Warning: Do Not energize the capacitor formore than 1 second at a time.3. Momentarily turn on the energizing cord (one second).4. Disconnect the energizing cord from the capacitor.5. If the field flash was successful, the generator shouldnow be producing approximately 240 VAC at the maincircuit breaker of the generator when the AUTO-OFF-MANUAL is set to the MANUAL position.*Warning: Do not field flash alternator morethan two times in sequence. if the unit hasnot produced power after two attempts, otherissues exist and need to be addressed.RESULTS:1. Refer back to flow chart.Page 52Part 2 AC GENERATORSsEctioN 2.4DiaGNostic tEsts0G9266revA.indd 52 10/15/2008 11:27:19 AM |
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