19 Flashcards
How is inherent overload protection provided in a motor?
Internal thermal overloads either embedded in or located near the motor windings
Relays are designed to control loads that draw less than 20A. Contactors are designed to control loads that draw more than 20A. T/F
T
Before restarting a motor that has been stopped for safety reasons, such as an overload, do not restart it immediately until what is performed?
Look around for the possible problem
The reserve capacity of a motor is expressed as a percentage above the FLA of the motor. A motor that has a service factor of 1.40 can operate at an amperage that is ______% higher than the nameplate operating current.
40%
What does a pilot-duty relay used for?
Designed for low level current switching on and off larger contacts or starters
A relay may have more than one type of contact configuration. T/F
T
What is used to determine the type of switching device used to start a motor?
The size of the motor and the application
Relays are often rated in horsepower. T/F
T
Normally closed contacts provide crankcase heat only during off cycle of the compressor. T/F
T
Why is cleaning motor starter contacts only a temporary measure?
It gets rid of the silver coating and speeds up deterioration
Resistance in the contact surface could cause the contacts to get hot. What
component of the contactor may be affected by the heat?
The springs tensions and the contact no contact pressure lessons.
What should be referenced when determining overload standards for all electrical
installations?
National electrical manufacturers association (NEMA)
What type of overload is very accurate and not affected by ambient temperature?
Magnetic overload devices
What can be used in place of the bimetal overload?
A solder pot
Fuses are used for motor protectors. T/F
F
What voltages can the holding coil on a contactor be designed for?
24, 115, 208 - 230 or 460v
What type of contactor is used to provide crankcase heat to the compressor?
Single contact single pole
The LRA rating can be as high as 7 times the FLA rating. T/F
T
