Unit 18 Application of Motors Flashcards
Is Luis an egg head
True or fals
True
Power supply data should include the following information
The voltage, the current capacity in amperes, the frequency in hertz (cps), and the phase (single or three).
The voltage range for an electric motor is usually within +or-
10%
If an electric motor is rated for 208 V, the maximum allowable voltage would be _____, and the minimum allowable voltage would be _____.
228.8 V, 187.2 V.
how a service technician can tell if a compressor motor is drawing the proper amperage when it is running.
The technician can take an amperage reading while the motor is operating under load and compare that reading to the FLA on the nameplate. * Also, he must know the operating conditions of the motor.
In the United States, the frequency in cycles per second (cps) at which an AC electric motor operates under normal conditions is
60
Three-phase motors are often used in air-conditioning systems in residences.
True or false
False
Two types of bearings commonly used on small motors are
Sleeve and ball bearings.
An open single-phase motor with a centrifugal starting switch may not be used in
An area where explosive gasses exist.
service factor of the motor is a multiplier applied to the motor HP. It indicates how much the motor can run overloaded on a continuous basis w/ out damaging the motor winding
True or false
True
How does the insulation factor of a motor affect its use?
The insulation type or class (factor) of a motor allows a motor to operate at higher or lower ambient temperatures.
A ______ bearing surface must be used in a vertical shaft motor application.
Thrust
Two primary electric motor mount characteristics are
Rigid mount and resilient mount (rubber).
NEMA has established standardized motor dimensions. NEMA stands for
National Electrical Manufacturers Association.
Two types of motor drives are
Belt drive and direct-drive (coupling or mounted to motor shaft).
What is a matched set of belts?
A matched set of belts means the belts are exactly the same length.
Name the different types of belts.
“A” width belts and “B” width belts. (OR smooth grip and “tractor tire” grip belts)
Why must direct-drive couplings be aligned?
If direct-drive couplings are out of alignment, vibration will occur, which results in excessive wear.
An instrument often used to check the alignment of two shafts is the
Dial indicator.
Why must resilient-mount motors have a ground strap?
If the motor were to have a ground (circuit from the hot line to the frame of the motor), the motor frame would be electrically hot w/ out the ground strap. (By rubber)
what is meant by the term rated-load amperage (RLA) as it applies to an compressor motor.
RLA is a mathematical calculation used to get UL approval for a compressor motor.
SFA
Surface factor amperage
FLA
Full-load amperage
RLA
Rated-low amperage
