NCCER Electrical Level 2 Module 2
Motors: Theory and Application Sections
1-6 Questions and Answers
The two primary types of motor enclosures classified by NEMA are ____. - ANS open
and totally enclosed
A
An open AC squirrel cage motor that makes use ofform-wound coils and an insulation
system is known asa(n) _____. - ANS sealed windings(type)
VI
The NEMA frame designation for gasoline pump motors is ____. - ANS G
TU
The letters FLA on a motor nameplate stand for ____. - ANS full-load amps
To determine the horsepower rating of a motor that is already installed and in place,
____. - ANS check the nameplate data
IS
Most industrial motors are NEMA Design ____. - ANS B
OM
The multiplier to the nameplate horsepower rating is called the _____. - ANS service
factor
The code requirements for motor disconnects are covered in ___. - ANS 430.102
NA
All motors must have a thermal protector if their voltage rating is greater than_____. -
ANS 600V-1,000V
To protect the motor from overloads and starting failures, use a ____. - ANS thermal
JP
protector
When studying the operation of electric motors, it is important to remember that
magnetic lines of force ____. - ANS do not cross
If a motor has 4 poles and is operating at a frequency of 60Hz, its synchronous speed is
_____. 120(60Hz)/4= 1,800 rpm - ANS 1,800 rpm
, The type of motor most likely to be used in a location with flammable dust and torque
fluctuations is a ____. - ANS squirrel cage induction motor
A heating system is most likely to use a _____. - ANS single-phase induction motor
With a constant-torque load, the horsepower ____. - ANS varies in direct proportion to
the speed
When variable-frequency speed control is used on a motor with a nameplate rating of
480V at 60Hz, the voltage-to-frequency ratio is ___. 480v/60hz=8 - ANS 8
A
When using a motor with dynamic braking, ____. - ANS electromechanical friction
VI
brakes may be required with large loads
A NEMA designation for a type of enclosed motor is _____. - ANS explosion-proof
TU
Using NEMA frame designations, the distance from the motor feet to the shaft center
line is known as ___. - ANS D dimension
IS
A motor with a NEMA kVA code letter of M has a locked-rotor value of ____. - ANS
10.0-11.9 kVA/hp
OM
A wye-connected motor has _____. - ANS the coils pointed in series
A delta-connected motor has ____. - ANS the coils connected in parallel
Any exposed live parts of motors must be guarded if the motor ____. - ANS operates
NA
at 50V or more between terminals
Per NEC Section 430.32, a motor with a service factor of 1.0 must trip at ____. - ANS
115% of the full-load current
JP
The most common class of insulation used in manufacturing and rewinding is NEMA
______. - ANS class B
When a single motor is supplied from a branch circuit, the ampacity of the branch circuit
must be _______ of the motor full-load current as determined by NEC Section
430.6(A)(1) - ANS no less than 12.5%
Motors: Theory and Application Sections
1-6 Questions and Answers
The two primary types of motor enclosures classified by NEMA are ____. - ANS open
and totally enclosed
A
An open AC squirrel cage motor that makes use ofform-wound coils and an insulation
system is known asa(n) _____. - ANS sealed windings(type)
VI
The NEMA frame designation for gasoline pump motors is ____. - ANS G
TU
The letters FLA on a motor nameplate stand for ____. - ANS full-load amps
To determine the horsepower rating of a motor that is already installed and in place,
____. - ANS check the nameplate data
IS
Most industrial motors are NEMA Design ____. - ANS B
OM
The multiplier to the nameplate horsepower rating is called the _____. - ANS service
factor
The code requirements for motor disconnects are covered in ___. - ANS 430.102
NA
All motors must have a thermal protector if their voltage rating is greater than_____. -
ANS 600V-1,000V
To protect the motor from overloads and starting failures, use a ____. - ANS thermal
JP
protector
When studying the operation of electric motors, it is important to remember that
magnetic lines of force ____. - ANS do not cross
If a motor has 4 poles and is operating at a frequency of 60Hz, its synchronous speed is
_____. 120(60Hz)/4= 1,800 rpm - ANS 1,800 rpm
, The type of motor most likely to be used in a location with flammable dust and torque
fluctuations is a ____. - ANS squirrel cage induction motor
A heating system is most likely to use a _____. - ANS single-phase induction motor
With a constant-torque load, the horsepower ____. - ANS varies in direct proportion to
the speed
When variable-frequency speed control is used on a motor with a nameplate rating of
480V at 60Hz, the voltage-to-frequency ratio is ___. 480v/60hz=8 - ANS 8
A
When using a motor with dynamic braking, ____. - ANS electromechanical friction
VI
brakes may be required with large loads
A NEMA designation for a type of enclosed motor is _____. - ANS explosion-proof
TU
Using NEMA frame designations, the distance from the motor feet to the shaft center
line is known as ___. - ANS D dimension
IS
A motor with a NEMA kVA code letter of M has a locked-rotor value of ____. - ANS
10.0-11.9 kVA/hp
OM
A wye-connected motor has _____. - ANS the coils pointed in series
A delta-connected motor has ____. - ANS the coils connected in parallel
Any exposed live parts of motors must be guarded if the motor ____. - ANS operates
NA
at 50V or more between terminals
Per NEC Section 430.32, a motor with a service factor of 1.0 must trip at ____. - ANS
115% of the full-load current
JP
The most common class of insulation used in manufacturing and rewinding is NEMA
______. - ANS class B
When a single motor is supplied from a branch circuit, the ampacity of the branch circuit
must be _______ of the motor full-load current as determined by NEC Section
430.6(A)(1) - ANS no less than 12.5%
