Guardian Technologies 4270 manual Test 3- Test Excitation Circuit Breaker

Section 7

DIAGNOSTIC TESTS

line voltage should read between 242-252 VAC. If voltage and frequency are good, no adjustment is needed. If voltage and frequency are low or high, proceed to next step.

4.Turn the governor adjusting screws to obtain a no-load frequen- cy as close as possible to 62-63 HERTZ. With no-load frequen- cy set, apply an electrical load as close as possible to the unit's rated load. Frequency with load applied should not fall below 58 HERTZ. If units frequency continues to drop below 58 HERTZ while under load, check for an overload condition.

TEST 3- TEST EXCITATION CIRCUIT

BREAKER

DISCUSSION:

This circuit breaker (CB2) 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 ( CB2) 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 equal to 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.

2A 2

2A

CB3

2

A. Schematic B. Pictorial

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

2.In the generator panel, locate the excitation circuit breaker. Disconnect Wire 2 and Wire 162 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 (CB2), 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.

CONNECT POSITIVE (+)			WIRE NO. 4
			TO ROTOR
BATTERY SUPPLY
	11		AND TO ECB
TO WIRE #4		22
			0
				6
				162

VOLTAGE

REGULATOR

TERMINALS

Figure 7-3. – Fixed Excitation Test

PROCEDURE:

1.Disconnect Wire 4 from the Voltage Regulator (VR). (Third ter- minal from the top of VR).

2.Connect a jumper wire to Wire 4 and to the 12 volt fused battery positive supply Wire 15 (Wire 15 located at fuse (F1) holder).

3.Set the VOM to measure AC voltage.

4.Disconnect Wire 2 from the DPE breaker (CB2) and connect one test lead to that wire. Disconnect Wire 6 from the Voltage Regulator and connect the other test lead to that wire. Start the generator and measure the AC voltage. It should be above 60 VAC. Record the results and stop the generator.

5.Re-connect Wire 2 to the DPE Circuit Breaker (CB2) and re-

connect Wire 6 to the Voltage Regulator.

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