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Generac Power Systems Recreational Vehicle Generator 5413 User Manual

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Section 3
INSULATION RESISTANCE TESTS

EFFECTS OF dIRT ANd MOISTURE

Moisture and dirt are detrimental to the continued

good operation of any generator set.
If moisture is allowed to remain in contact with the

Stator and Rotor windings, some of the moisture will

be retained in voids and cracks of the winding insula-

tion. This will result in a reduced Insulation resistance

and, eventually, the unit’s AC output will be affected.
Insulation used in the generator is moisture resistant.

However, prolonged exposure to moisture will gradu-

ally reduce the resistance of the winding insulation.
Dirt can make the problem worse, since it tends to

hold moisture Into contact with the windings. Salt, as

from sea air, contributes to the problem since salt can

absorb moisture from the air. When salt and moisture

combine, they make a good electrical conductor.
Because of the detrimental affects of dirt and mois-

ture, the generator should be kept as clean and as

dry as possible. Rotor and Stator windings should be

tested periodically with an insulation resistance tester

(such as a megohmmeter or hi-pot tester).
If the Insulation resistance is excessively low, drying

may be required to remove accumulated moisture.

After drying, perform a second insulation resistance

test. If resistance is still low after drying, replacement

of the defective Rotor or Stator may be required.

INSULATION RESISTANCE TESTERS

Figure 3-1 shows one kind of hi-pot tester. The tester

shown has a “Breakdown” lamp that will glow during

the test procedure to indicate an insulation breakdown

in the winding being tested.

Figure 3-1. – One Type of Hi-Pot Tester

*

DANGER! INSULATION RESISTANCE

TESTERS SUCH AS HI-POT TESTERS AND

MEGOHMMETERS ARE A SOURCE OF HIGH
AND DANGEROUS ELECTRICAL vOLTAGE.
FOLLOW THE TESTER MANUFACTURER’S
INSTRUCTIONS CAREFULLY. USE COMMON
SENSE TO AvOID DANGEROUS ELECTRICAL
SHOCK

dRYINg THE gENERATOR

GENERAL:
If tests indicate the insulation resistance of a winding

is below a safe value, the winding should be dried

before operating the generator. Some recommended

drying procedures include (a) heating units and (b)

forced air.

HEATING UNITS:
If drying is needed, the generator can be enclosed in

a covering. Heating units can then be installed to raise

the temperature about 15°-18° F (8°-10° C) above

ambient temperature.

FORCED AIR:
Portable forced air heaters can be used to dry the

generator. Direct the heated air into the generator’s

air intake openings. Remove the voltage regulator and

run the unit at no-load. Air temperature at the point

of entry into the generator should not exceed 150° F.

(66° C.).

CLEANINg THE gENERATOR

GENERAL:
The generator can be cleaned properly only while it is

disassembled. The cleaning method used should be

determined by the type of dirt to be removed. Be sure

to dry the unit after it has been cleaned.
NOTE: A shop that repairs electric motors may

be able to assist you with the proper cleaning of

generator windings. Such shops are often expe-

rienced in special problems such as a sea coast

environment, marine or wetland applications, min-

ing, etc.

USING SOLVENTS FOR CLEANING:
If dirt contains oil or grease a solvent is generally

required. Only petroleum distillates should be used to

clean electrical components. Recommended are safe-

ty type petroleum solvents having a flash point greater

than 100° F. (38° C.).

*

CAUTION!: Some generators may use epoxy

or polyester base winding varnishes. Use sol-

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