Generac Power Systems 65, 55, 75 Test 8- Check Sensing Leads / Power Windings, 11S 22S, Model Ohms

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Section 7

DIAGNOSTIC TESTS

PROCEDURE:

1.Disconnect Wire 2 from the Excitation Circuit Breaker.

2.Disconnect Wire 6 from the Voltage Regulator.

3.Set a VOM to its “Rx1” scale and zero the meter.

4.Connect the VOM test leads across the terminal ends of Wires 2 and 6. The VOM should indicate the resistance of the Stator Excitation (DPE) Windings.

EXCITATION “DPE” WINDING RESISTANCE *

(Measured Across Wires 2 & 6)

MODEL

OHMS

QP55 (4702/4703)

1.41Ω − 1.63Ω

QP65 (4704/4705)

1.59Ω − 1.84Ω

QP75 (4706/4707)

1.12Ω − 1.30Ω

*Resistance values In ohms at 20° C. (68° F.). Actual readings may vary depending on ambient temperature. A tolerance of plus or minus 5% is allowed.

5.Now, set the meter to its “Rx1 K” or “Rx10,000” scale and zero the meter. Test for a “short-to-ground” condition as follows:

a.Connect one meter test lead to Stator lead No. 2, the other test lead to a clean frame ground.

b.The meter should read “Infinity”. Any other read- ing indicates a “short-to-ground” condition and the Stator should be replaced.

6.Test for a short between windings as follows:

a.Meter should be set to its “Rx1 K” or “Rx10,000” scale.

b.Connect one meter test lead to Stator Wire 2, the other test lead to Stator lead No. 11. The meter should read “Infinity”.

c.Connect one VOM test lead to Stator lead No. 2 the other test lead to Stator lead No. 33. “Infinity” should be indicated.

d.Connect one VOM test lead to Stator lead No. 2 and connect the other test lead to Stator lead No. 66. “Infinity” should be indicated.

RESULTS:

1.If the Stator excitation (DPE) windings are open or shorted, replace the Stator assembly.

2.If the excitation windings are good, perform “Insulation Resistance Test”, page 13.

TEST 8- CHECK SENSING LEADS / POWER

WINDINGS

DISCUSSION:

The Voltage Regulator “regulates” excitation current flow to the Rotor by electronically comparing sensing

voltage to a pre-set reference voltage. The sensing voltage is delivered to the Voltage Regulator via Wires 11S and 22S.

If an open circuit exists in sensing leads 11S or 22S, the normal reaction of an unprotected Regulator would be to increase the excitation current to the Rotor in an effort to increase the actual AC output voltage. This would result in a “full field” condition and an extremely high AC output voltage.

To protect the system against such a high AC output voltage, the Voltage Regulator will shut down if sens- ing voltage signals are lost.

If the regulator shuts down, the generator's AC output voltage will decrease to a value that is commensurate with the Rotor's residual magnetism (about 5-12 VAC).

PROCEDURE:

Gain access to the generator control panel interior. Test the Stator power windings, as follows:

1.From main breaker, disconnect Wires 11 P and 33.

2.Also disconnect Wires 22P and 44 from the ground terminal.

3.Disconnect Wires 11S and 22S from the Voltage Regulator.

4.Set a VOM to its “Rx1” scale and zero the meter.

5.Connect the meter test leads across Stator leads 11P and 22P. Normal power winding resistance should be read.

6.Connect the meter test leads across Stator leads 33 and 44. Normal power winding resistance should be read.

7.Connect the meter test leads across Stator leads 11S and 22S. Normal Power Winding resistance should be read.

AC POWER WINDING RESISTANCE * QP55 (Model 4702/4703)

ACROSS WIRES:

OHMS

11P & 22P

0.28Ω − 0.32Ω

11S

& 22S

0.28Ω − 0.32Ω

33

& 44

0.28Ω − 0.32Ω

 

 

AC POWER WINDING RESISTANCE * QP65 (Model 4704/4705)

ACROSS WIRES:

OHMS

11P & 22P

0.209Ω − 0.242Ω

11S

& 22S

0.209Ω − 0.242Ω

33

& 44

0.209Ω − 0.242Ω

 

 

AC POWER WINDING RESISTANCE * QP75 (Model 4706/4707)

ACROSS WIRES:

OHMS

11P & 22P

0.157Ω − 0.182Ω

11S

& 22S

0.157Ω − 0.182Ω

33

& 44

0.157Ω − 0.182Ω

*Resistance values In ohms at 20° C. (68° F.). Actual readings may vary depending on ambient temperature. A tolerance of plus or minus 5% is allowed.

8.Now, set the VOM to its “Rx1 K” or “Rx10,000” scale and zero the meter.

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Contents Diagnostic Repair Manual Safety Replacement PartsTable of Contents Section Specifications & Charts Section Exploded Views / Part NumbersElectromagnetic Induction MagnetismElectromagnetic Fields Simple AC Generator More Sophisticated AC GeneratorGenerator Operating Diagram Line Breakers 120 Volts only Field BoostGenerator AC Connection System Connection for 120 Volts Only Reconnection for Dual Voltage OutputRotor Assembly Stator AssemblyBattery Charge Components Brush HolderExcitation Circuit Components GeneralAdjustment Procedure Crankcase BreatherVoltage Regulator DescriptionInstall Breather Install oil vapor collector and retainerControl Panel Component Identification Check BreatherCleaning the Generator Effects of Dirt and MoistureInsulation Resistance Testers Drying the GeneratorBrushing and Vacuum Cleaning Stator Insulation ResistanceCloth or Compressed AIR Stator SHORT-TO-GROUND TestsTesting Rotor Insulation Testing Stator InsulationTesting Rotor Insulation MegohmmeterMeters VOMMeasuring AC Voltage Measuring DC VoltageMeasuring Resistance Measuring AC FrequencyMeasuring Current Electrical Units Ohms LAWAmpere VoltCircuit CONDITION- Rest IntroductionOperational Analysis Circuit CONDITION- Priming Circuit CONDITION- Cranking Circuit CONDITION-RUNNING Choke Heater CHCircuit CONDITION- Shutdown Circuit CONDITION- Fault Shutdown Sure Switch LOPBattery Recommended BatteryBattery Cables Engine Controller Circuit BoardAMP Fuse Fuel Primer SwitchSTART-STOP Switch Starter Contactor Relay Starter Motor Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Troubleshooting Flowcharts Procedure Test 1- Check NO-LOAD Voltage FrequencyTest 2- Check Engine Governor DiscussionGovernor Adjustment Test 3- Test Excitation Circuit BreakerTest 4- Fixed Excitation TEST/ROTOR AMP Draw If continuity was indicated, go to TestTest 5- Wire Continuity Re-connect Wire 11 and Wire 22 to the Voltage RegulatorSet the VOM to measure AC voltage Set a VOM to its Rx1 scaleIf field boost checks good, replace the Voltage Regulator Test 6- Check Field BoostTest 7 Test Stator DPE Winding Test 8- Check Sensing Leads / Power Windings Across Wires Ohms11S 22S Model OhmsTest 9- Check Brush Leads Test 10 Check Brushes & Slip RingsTest 11- Check Rotor Assembly Tance Tests ProcedureTest 12 Check Main Circuit Breaker Replace the Rotor if it fails the testTest 15 Check Battery Charge Output Test 16 Check Battery Charge RectifierBattery Charge Rectifier BCR is a full wave rectifier Test 13- Check Load Voltage Frequency10. Battery Charge Rectifier Short to GroundTest 19- Test Primer Switch Set a VOM to read battery voltage 12 VDCAlso see Fuel Primer Switch, Test 18 TRY Cranking the EngineTest 20- Check Fuel Pump 13. The LPG Fuel Solenoid FSTest 21- Check 7.5 AMP Fuse Test 22- Check Battery & CablesTest 23- Check Power Supply to Circuit Board Test 24 Check START-STOP Switch 17. Start-Stop SwitchTest 26- Check Starter Contactor Relay Set a VOM to measure DC voltage 12 VDCConditions Affecting Starter Motor Performance Test 26A Check Starter ContactorTest 27 Check Starter Motor Checking the Pinion Tools for Starter Performance TestMeasuring Current TachometerTesting Starter Motor Test 28- Check Fuel SupplyTest Bracket Remove Starter Motor28 LP Gas Carburetion Diagram Discussion LPG ModelsTest 29 Check Wire 14 Power Supply Test 30 Check WireBattery voltage is not measured, proceed to Step Crank the engine. The meter should indicate battery voltageTest 31 Check Fuel Solenoid Gasoline Models Test 32 Check Ignition SparkCylinder Balance Test Conclusion No cylinder is weakest of the two cylindersTest 34 Check and Adjust Ignition Magnetos Test 33 Check Spark Plugs37. Setting Ignition Magneto Armature Air Gap Test 35 Check Valve Adjustment Adjusting Valve ClearanceChecking Flywheel Magnet Flywheel KEYTest 37 Check Choke Solenoid Install Rocker ARM CoverTest 36 Check Carburetion 43. Connector Adjust the regulated pressure on the gauge to 80 psi Down Test / Compression TestRepeat Steps 1 through 8 on remaining cylinder Check CompressionIf all steps check GOOD, go to Test Test 39 Check OIL Pressure SwitchTest 40 Test OIL Temperature Switch Short to Ground Test 41 Test Choke HeaterTest 42 Check LPG Fuel Solenoid 49. Fuel Solenoid Major Disassembly ENCLOSURE/PANEL RemovalStator Removal Rotor RemovalStarter Removal Belt TensioningEngine Removal FLYWHEEL/MAGNETO Removal Page Section Exploded Views / Part Numbers Part NO. QTY Description Enclosure Drawing No E1011-B QTY Description Sheet Metal Drawing No E1012-E QTY Description Flywheel Assy GT-990Control Panel Drawing No E1013-A Wire ASM GRD STD Conn Switch Spdt ON-MOM-ONSwitch 6A Spdt Not Shown PANEL, TOP ControlTwin Engine Drawing No E1014-B ASSEMBLY, Crankcase RV ASSEMBLY, BreatherASSEMBLY, Head #1 ASSEMBLY, OIL Fill CAPLP Regulator Drawing No E1530 CASTING, Twin Regulator Housing Washer Flat M4SOLENOID, Twin Regulator SPRING-SOLENOID PlungerSpecifications & Charts Generator Specifications Nominal Resistances of Generator Windings AT 68FEngine Speeds and Voltage Specifications Page Electrical Data Electrical Data PO BOX 297 WHITEWATER, WI

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