20 Flashcards
(33 cards)
If a condenser fan motor grounds out, it will usually
trip a circuit breaker to shut off the unit
If a motor hums but does not start, there is a potential problem
with the start components, with an open winding,
with insufficient supply voltage
If the evaporator fan motor has an open run-winding and is not operating but the compressor continues to run, the
evaporator will ice up.
What does the marked terminal on a run capacitor mean/indicate?
Where to attach power
If a run capacitor is subjected to overcurrent, it will have a bulge in the vent at
the top of the container. T/F
F
Good motor windings should have a resistance value of a minimum of 100
megaohms to ground relative to ground. T/F
T
A digital multimeter can be used in place of a megger as a last resort. T/F
F
A decrease in resistance in the start winding may prevent a motor from starting. T/F
T
If the cost of repairing a motor is close to the cost of replacing the motor, It is better to replace the motor. T/F
T
When sleeve bearings fail, they normally lock up (will not turn). T/F
T
A low force reading on a belt tension gauge is an indication that the belt is too T/F
F
Motor bearing failure is considered a mechanical problem. T/F
T
A motor may not start if the load is too great. T/F
T
The proper way to discharge a capacitor is to place a 10,000 D, 5 watt resistor
across both capacitor terminals. T/F
F
An open start winding will not affect the readings between the run to start T/F
F
The large o-ring on the belt tension gauge measures the pounds of force when
the gauge is pressed against the belt. T/F
F
What are the three common electrical motor problems?
Open winding, shortage, grounded.
How can motor bearing failure with roller and ball bearings be identified?
Sounds and roughness
Belts that are too loose may cause what type of problems?
Too much slip
How are most assemblies held to the motor shaft?
Set screw/ keyway
Provides a better bond between the motor and whatever assembly is attached to the shaft.
Keyway
When a 3-phase motor is trying to run on two power lines instead of three (L1 &
L2 & L3)
Single phasing
Frame of the motor or earth ground through the building electrical system.
Ground earth
Electrical meter used to check resistance, condition of motor windings, condition
of refrigeration and oil environments around motor windings.
Megger
