Guardian Technologies 4270 manual Test 2 Check & Adjust, Test 1- Check NO-LOAD Voltage Frequency

	Section 7
	DIAGNOSTIC TESTS
INTRODUCTION	3. If AC output voltage and frequency are both “zero”, go to Test 12.
The “Diagnostic Tests” in this chapter may be per-	4. If the no-load voltage and frequency are within the stated limits,
formed in conjunction with the “Flow Charts” of	go to Test 13.
Section 6. Test numbers in this chapter correspond to	NOTE: The term “low voltage” refers to any volt-
the numbered tests in the “Flow Charts”.
	age reading that is lower than the unit's rated volt-
Tests 1 through 17 are procedures involving problems
	age. The term “residual voltage” refers to the out-
with the generator's AC output voltage and frequency	put voltage supplied as a result of Rotor residual
(Problems 1 through 4 in the “Flow Charts”).	magnetism (approximately 5-12 VAC).
Tests 18 through 42 are procedures involving prob-
lems with engine operation (Problems 5 through 9 in	TEST 2 - CHECK & ADJUST
the “Troubleshooting Flow Charts”).
	ENGINE GOVERNOR
Review and become familiar with Section 4,
“Measuring Electricity”.

NOTE: Test procedures in this Manual are not nec- essarily the only acceptable methods for diagnos- ing the condition of components and circuits. All possible methods that might be used for system diagnosis have not been evaluated. If any diagnos- tic method other than the method presented in this Manual is utilized, ensure that neither personnel safety nor the product's safety will be endangered by the procedure or method utilized.

TEST 1- CHECK NO-LOAD VOLTAGE AND

FREQUENCY

DISCUSSION:

The first step in analyzing any problem with the AC generator is to determine the unit's AC output voltage and frequency.

PROCEDURE:

1.Set a volt-ohm-milliammeter (VOM) to read AC voltage. Connect the meter test leads across customer connection leads T1 (Red) and T2 (White).

2.Disconnect or turn OFF all electrical loads. Initial checks and adjustments are accomplished at no-load.

3.Start the engine, let it stabilize and warm up.

4.Read the AC voltage.

5.Connect an AC frequency meter across AC output leads T1 (Red) and T2 (White) on the customer connection. Repeat the above procedure.

RESULTS:

For units rated 60-Hertz, no-load voltage and frequen- cy should be approximately 122-126 VAC and 61-63 Hertz respectively.

DISCUSSION:

Rotor operating speed and A/C output frequency is proportional. The generator will deliver a frequency of 60 HERTZ at 1950 RPM or 62 HERTZ at 2015 RPM. The voltage regulator should be adjusted to deliver 120 VAC (line-to-neutral) at a frequency of 60 HERTZ or 124 VAC (line-to-neutral) at 62 HERTZ. It is appar- ent that if governor speed is high or low, A/C frequen- cy and voltage will be correspondingly high or low. Governor speed at no-load is usually set slightly above the rated speed of 60HERTZ (to 62.8 HERTZ) to prevent excessive RPM, frequency, and voltage droop under heavy electrical loading.

ENGINE GOVERNOR ADJUSTMENT:

Initial adjustment of governed speed should be accomplished at no-load condition. Prior to engine startup, turn off all electrical loads by whatever means available (such as generator main circuit breaker).

Figure 7-1. – Governor Adjustment Points

1.	If AC voltage and frequency are BOTH correspondingly high or	PROCEDURE:
	low, go to Test 2.	1.	Connect an accurate A/C frequency meter and voltmeter to the
2.	If AC frequency is good but low or residual voltage is indicated,		proper generator leads.
	go to Test 3.	2.	Start the engine, let it stabilize and warm up at no-load.
		3.	Frequency meter should read between 62-63 HERTZ. Line-to-

Page 37