Generac Power Systems 65, 55 TEST 3- TEST EXCITATION CIRCUIT BREAKER, 3.- Fixed Excitation Test

Section 7

DIAGNOSTIC TESTS

GOVERNOR ADJUSTMENT

1.Loosen the GOVERNOR CLAMP BOLT.

2.Push Spring end of GOVERNOR LEVER clockwise to wide open throttle position of lever.

a.Hold the GOVERNOR LEVER at wide open throttle and, with a pair of pliers, rotate the GOVERNOR SHAFT fully clockwise (CW). Use a minimum amount of force against the gover- nor shaft.

b.While holding the GOVERNOR SHAFT fully clockwise and the GOVERNOR LEVER at wide open throttle, tighten the GOVERNOR CLAMP BOLT to 70 inch-pounds (8 N-m).

3.Start engine, let it stabilize and warm up at no-load.

4.Turn the ADJUSTER NUT to obtain a frequency reading of 62 Hertz.

5.Determine if the GOVERNOR SPRING is properly located in the slot of the GOVERNOR LEVER as follows:

a.If droop is excessive, move the GOVERNOR SPRING down one slot on LEVER.

b. For greater stability, move the GOVERNOR SPRING up one slot on LEVER.

6.After repositioning the SPRING on a LEVER slot, recheck fre- quency reading and, if necessary, readjust ADJUSTER NUT to obtain 62 Hertz at no-load.

7.When frequency is correct at no-load, check the AC voltage reading. If voltage is incorrect, the voltage regulator may require adjustment. See “VOLTAGE ADJUSTMENT,” Page 10.

TEST 3- TEST EXCITATION CIRCUIT

BREAKER

DISCUSSION:

This circuit breaker (CB3) is normally closed and self- resetting. It will open in the event of excessive current from the Stator excitation (DPE) winding. The circuit breaker should re-close or reset automatically after it cools down (takes approximately two minutes).

When the breaker (CB3) is open, excitation current to the Regulator (and to the Rotor) will be lost. The unit's AC output voltage will then drop to a value that is commensurate with the Rotor's residual magnetism (about 5-12 volts AC). This test will determine if the breaker has failed in its open position.

PROCEDURE:

Note: After running the unit, allow two minutes for the breaker to reset.

1.Set a volt-ohm-milliammeter (VOM) to its “Rx1” scale and zero the meter.

Figure 7-2. – Excitation “DPE” Circuit Breaker

2.In the generator panel, locate the excitation circuit breaker. Disconnect Wire 2 and Wire 2A from the breaker terminals.

3.Connect the meter test leads across the two circuit breaker (CB3) terminals. The meter should indicate “continuity”.

RESULTS:

1.If the meter did NOT read “continuity”, replace the excitation (DPE) circuit breaker (CB3), and go to Test 4.

2.If “continuity” was indicated, go to Test 4.

TEST 4- FIXED EXCITATION TEST/ROTOR

AMP DRAW

DISCUSSION:

The fixed excitation test consists of applying battery voltage (12 VDC) to the Rotor windings. This allows that portion of the excitation circuit between the Voltage Regulator and the Rotor (including the Rotor itself) to be checked as a possible cause of the prob- lem. When battery voltage is applied to the Rotor, the resulting magnetic field around the Rotor should induce a Stator power winding voltage equal to about one-half the unit's rated output voltage.

Figure 7-3. – Fixed Excitation Test

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