Intake Heater Switch; Servicing The Alternating Current Generator; Preventative Maintenance And Operating Precautions; Generator Repair/Test Procedures - Carrier TRANSICOLD 69UG15 Series Operation And Service

4.4.16 Intake Heater Switch

a. Remove control box cover.
b. Remove all connections going to heater switch (HS).
c. Remove heater switch from control box.
d. Install new heater switch.
e. Reconnect wire harness connections to switch.
f. Confirm that wires are connected to correct termin-
als.
g. Reinstall control box cover.
4.5 SERVICING THE ALTERNATING CURRENT
GENERATOR
4.5.1 Preventative Maintenance and
Operating Precautions
Costly repairs and down time can usually be prevented
by operating electrical equipment under conditions that
are compatible with those under which the equipment
was designed. Follow the instructions outlined below to
insure maximum efficiency of the electrical equipment.
a. Cooling
Keep all cooling parts clean. DO NOT EXCEED
TEMPERATURE RISE OF 80C (176F) ABOVE A 40C
(104F) AMBIENT. This ensures that the NEMA Class
"F" insulation will not be damaged. DO NOT EXCEED
RATED LOAD except as specified for the equipment.
OPERATE GENERATOR AT RATED SPEED. Failure
to operate generators at rated load or speed will cause
overheating and possible damage to windings due to
over voltage or current.
b. Generator Windings (Drying)
WARNING
Do not direct water or steam into the gener-
ator 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 ob-
serving 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.

4.5.2 Generator 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.
When trying to restore residual magnetism,
be sure to wear safety glasses and non-con-
ductive 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.
4−5
CAUTION
T-343