Page 44 - Offshore Electrical Engineering Manual

Typical Alternator Heat Run Procedure 31

of the test. If the conditions are such that parts of a machine are in a position
in which ventilation may be impeded, e.g., in a pit, the air temperature in such
a restricted area is deemed to be the ambient temperature. If the air is admitted
into a machine through a definite inlet opening or openings, the temperature of
the cooling air should be measured in the current of air at or near its entry to the
machine.

TYPICAL ALTERNATOR HEAT RUN PROCEDURE

The test is carried out at zero power factor lagging to avoid the need for a large
prime mover. The normal safety precautions for testing electrical machinery should
be taken.

1. Test Equipment
a. An ac voltmeter is required to be connected across the alternator output

terminals.
b. Two ac ammeters with suitable current transformers (CTs) are required for

monitoring the alternator output current.

c. Two single phase wattmeters with suitable voltage and current inputs are
required.

d. A Tachometer suitable for the generator speed at operating frequency is
needed.

e. A dc ammeter placed in series with the exciter field is required

f. A dc voltmeter with fused leads, placed across the exciter field, is needed.

g. Portable (digital probe) thermometers for internal temperature measurement
are needed.
h. Portable thermometers for air temperatures

i. A driving motor capable of maintaining the rated speed at full load (zero

p.f.), 150 & load for 15 s and 25% overspeed is required.

j. Adjustable 3 phase reactors are needed

k. Load circuit breaker is needed.
2. Method

a. Connect the above list of equipment.
b. Couple the alternator to the drive motor and fit an adequate guard over the

coupling and exposed shaft.

c. Check that the alternator enclosure is as specified by the customer, is com-
plete and fitted correctly.

If terminal box lids connections cannot be fitted after making test connections,
seal box and cable outlets with paper and masking tape.
Calculate the expected ammeter and wattmeter readings from the CT ratios.
Run generator at rated speed (if possible, plus 4.0%) and record no load reading
using the appropriate Test Sheet. Apply the load and continue the run, recording all
readings every 60 min for at least 4 h or until thermal stability is reached.