Unit 19 Motor Controls Flashcards
The recommended repair for a defective relay is to. A. Replace it. B. Send it to repair shop. C.Fix it your self. D. None of the above.
A. Replace it
The two types of relays are _______ and ______.
Light duty (switching) and Heavy duty (starting).
. The two amperages that influence the choice for replacing a motor starter are _______ and ________
FLA and LRA
FLA means?
Full load amperage
LRA means?
Locked-rotor amperage
What is the difference between a contactor and a starter?
A starter has overload protection devices, while a contactor doesn’t.
True or False: A contactor can always be converted to a starter.
False
What are the contact surfaces of relays contactors, and starters made of?
Silver. (Alloys)
What causes an overload protection device to function?
An overload protection device will disconnect the motor at some current draw value that is slightly more than the FLA value so that the motor can be operated at it’s fill-load design capacity
What is not a typical operating voltage used for relays, contactors, and motor starters? A. 12 V B. 24 V C. 115 V D. 230 V
12 V.
Why is it not a good idea to file or sand the contactor contacts?
Filing or sanding exposes the base metals under the silver plating and speeds deterioration.
Why is it not a good idea to use circuit protection devices to protect large motors from overload conditions?
The motor may be operating at an overload condition that may not cause the conductor to be overloaded.
Under what conditions are motors allowed to operate with slightly higher-than-design loads?
The motor can operate above the FLA and within the service factor without harm, for a limited time.
Under what conditions are motors allowed to operate with slightly higher-than-design loads?
The motor can operate above the FLA and within the service factor without harm, for a limited time
What is the purpose of overload protection at the motor?
To prevent the motor from overheating and damaging itself.
True or False A motor can be restarted immediately after it has stopped or been overloaded.
False
Dirty and pitted contacts in a contactor can?
Cause resistance and heat.
The moving armature in a contactor is actuated by
The solenoid coil.
Crankcase heat for compressors is often controlled by using
Auxiliary contacts.
The service factor of an electric motor is determined by the
Motors reserve capacity
The contactor is a ______ with electrical contacts.
Magnetic coil.
If the relay does not operate properly
It must be replaced.
Release are designed to control loads that drawn less than ______of electric current
20 A
what is considered a throwaway device because parts are not available for rebuilding it when it’s no longer functions properly
A. Relay
B. Compressor
C. Filter
D. Console
Relay
the ______has a magnetic coil that opens or closes one or more sets of contacts
Relay
What is typically used for starting a motor that has a
A general-purpose relay
= true or false. are switching relay suitable to starting Motors
False
because they have more resistance in the context
the pilot Duty relay contents are often made of a
find silver alloy
design for low-level current switching
the LRA of a motor is typically five times higher than the ________ of the motor and can be as high as seven times the____
FLA for both
The ______ is a large version of a relay. It can be rebuilt if it fails
Contactor
The motor starter differs from a contactor because the motors ______________ built into its framework
Overload protection
NEC means
Nation electrical code
Bimetal and solder-pot device’s ________ operated
Thermally
