Carrier 69UG15 b. Generator Windings Drying, c. Rotor Damage, d. Terminal Strip Cleaning, Wire

b. Generator Windings (Drying)

WARNING

Do not direct water or steam into the generator openings. Do not allow any soap and water solutions to enter the alternator.

WARNING

High voltage (dielectric) testing must not be performed to the machine without first observing NEMA rules. The insulation of this generator winding may be safely checked by using a megger. A high megger reading indicates good insulation.

Generators that have been in transit, recently steam cleaned or in storage for long periods may be subjected to extreme temperature and moisture changes. This can cause excessive condensation, and the generator windings should be thoroughly dried out before bringing the generator up to full nameplate voltage. If this precaution is not taken, serious damage to the generator can result. The following steps should be taken to effectively dry the generator windings:

1.Dry windings by placing generator in drying oven or hot room, or dry with warm air blower directed through windings.

2.If the generator has been operated and is being placed into storage for any period of time, a P.D. George #11127 type air-dry fungus resistant varnish should be applied.

The finest insulation job can be very quickly broken down by carelessly applying high voltage to windings in a moisture saturated condition. Failure to follow these guidelines could easily cause a breakdown, making it necessary to return the generator to the factory for repair.

c. Rotor Damage

If a rotor becomes defective, it should be returned to the factory with full nameplate data. To repair a rotor, the special tooling and technique of the factory are necessary and essential. Should a failure occur, Carrier Transicold should be notified immediately and steps will be taken to return the generator for service.

d. Terminal Strip Cleaning

Open terminal box. Remove dust and debris, and clean terminal strip with wire brush. Reapply protective coating.

4.5.2Generator Repair/Test Procedures a. Restoring Residual Magnetism

The direct current (DC) necessary to magnetize the alternator field is obtained from the exciter. Initially, upon starting the generator, current flow and voltage are induced into the exciter armature by the magnetic lines of force set up by the residual magnetism of the exciter field poles.

Residual magnetism of the exciter field poles may be lost or weakened by a strong neutralizing magnetic field from any source, or if the generator is not operated for a long period of time.

Should the generator fail to build up voltage after being disassembled for any reason, a momentary short-circuit of any two generator leads (L1, L2 and L3) while generator is running should be sufficient to correct this condition.

CAUTION

When trying to restore residual magnetism, be sure to wear safety glasses and non-conductive gloves. Use an insulated 12 gauge (or higher) jumper wire. Cut off all but a few strands from both ends of the jumper wire to help prevent fusing.

As an alternate method, apply either an alternating current or a direct current voltage of approximately 20 volts to any two generator leads (L1, L2 and L3) while generator is running. Do not make a positive connection, but rather touch the leads together until the generator voltage begins to rise, then remove. Insert a 30 ampere fuse into the circuit to prevent any damage in case the build-up voltage is not removed quickly enough. Reflash field if generator output voltage does not build up.

b. Winding Insulation Testing

Continuity test results for the stator winding tests are provided in the following table:

Wire	Ohm*	Wire	Ohm*	Wire	Ohm*
Pair		Pair		Pair
T10-T1	I	T1-T8	I	T4-T5	I
T10-T2	I	T1-T9	I	T4-T6	I
T10-T3	I	T2-T3	I	T4-T7	I
T10-T4	I	T2-T4	I	T4-T8	I
T10-T5	I	T2-T5	0	T4-T9	I
T10-T6	I	T2-T6	I	T5-T6	I
T10-T7	0	T2-T7	I	T5-T7	I
T10-T8	0	T2-T8	I	T5-T8	I
T10-T9	0	T2-T9	I	T5-T9	I
T1-T2	I	T3-T4	I	T6-T7	I
T1-T3	I	T3-T5	I	T6-T8	I
T1-T4	0	T3-T6	0	T6-T9	I
T1-T5	I	T3-T7	I	T7-T8	0
T1-T6	I	T3-T8	I	T7-T9	0
T1-T7	I	T3-T9	I	T8-T9	0

* 0 = no resistance (closed circuit) & I = infinite resistance (open circuit)

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