NCCER Electrical Level 2 Module 2
Motors: Theory and Application
Questions and Answers
Question : How DC motors operate?
CORRECT ANSWER : Magnetic lines of force are
continuous and always form closed loops; Magnetic lines of force do not cross.
Question : Armature
CORRECT ANSWER : The rotating windings of a DC
motor.
Question : Commutator
CORRECT ANSWER : A device used on electric motors or
generators to maintain a unidirectional current.
Question : Torque
CORRECT ANSWER : _____ is produced by mounting a
loop in a fixed magnetic field and as long as the fields of the magnet and armature interact.
Question : horsepower
CORRECT ANSWER : The rated output capacity of the
motor. It is based on breakdown torque, which is the maximum torque a motor will develop without an abrupt drop in speed.
Question : magnetic field
CORRECT ANSWER : A _____ is produced by the fields
poles, and a loop of wire in the armature turns and cuts this magnetic field.
Question : Horsepower: (Equation)
CORRECT ANSWER : Watts/746
Question : Types of DC motors
CORRECT ANSWER : Shunt
Series Compound
Question : Types of AC motors
CORRECT ANSWER : Synchronous and Induction (Single
and Polyphase)
Question : Periodic duty: (Definition)
CORRECT ANSWER: Intermittent operation at a
substantially constant load for a short and definitely specified time.
Question : Revolutions per minute (rpm)
CORRECT ANSWER : The approximate full-load speed at
the rated power line frequency. The speed of a motor is determined by the number of poles in the winding.
Question : Rotation
CORRECT ANSWER : For single-phase motors, the
standard rotation, unless otherwise noted, is counterclockwise facing the lead or opposite shaft end. All motors can be reconnected at the terminal board for opposite rotation unless other wise indicated.
Question : Synchronous speed
CORRECT ANSWER : The speed of the revolving field of
the stator, which is dependent on the supply frequency and number of poles in a stator winding.
Question : Field poles
CORRECT ANSWER : The stationary portion of a DC
motor that produces the magnetic field.
Question : The principle reason for developing the brushless
DC motor was to ___.
CORRECT ANSWER : eliminate commutator problems
Question : The electrical energy required to produce 1hp of
mechanical energy is _____.
CORRECT ANSWER : 746W
Question : When there is a wide variation in both torque and
speed requirements, such as a blower or hoist, use a _____.
