NCCER Electrical Level 2 Module 2
Motors: Theory and Application
How DC motors operate? - Answer- Magnetic lines of force are continuous and
always form closed loops; Magnetic lines of force do not cross.
Armature - Answer- The rotating windings of a DC motor.
Commutator - Answer- A device used on electric motors or generators to maintain a
unidirectional current.
Torque - Answer- _____ is produced by mounting a loop in a fixed magnetic field
and as long as the fields of the magnet and armature interact.
horsepower - 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.
magnetic field - Answer- A _____ is produced by the fields poles, and a loop of wire
in the armature turns and cuts this magnetic field.
Horsepower: (Equation) - Answer- Watts/746
Types of DC motors - Answer- Shunt
Series
Compound
Types of AC motors - Answer- Synchronous and Induction (Single and Polyphase)
Periodic duty: (Definition) - Answer- Intermittent operation at a substantially constant
load for a short and definitely specified time.
Revolutions per minute (rpm) - 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.
Rotation - 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.
Synchronous speed - 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.
Field poles - Answer- The stationary portion of a DC motor that produces the
magnetic field.
, The principle reason for developing the brushless DC motor was to ___. - Answer-
eliminate commutator problems
The electrical energy required to produce 1hp of mechanical energy is _____. -
Answer- 746W
When there is a wide variation in both torque and speed requirements, such as a
blower or hoist, use a _____. - Answer- series DC motor
The name of the stationary motor part that produces the magnetic field during
operation is the ____. - Answer- stator
The rpm of a 60Hz motor with two poles is ___. - Answer- 3,600rpm
In three-phase motors, the rotor most commonly used is the _____. - Answer-
squirrel cage rotor
The starting torque characteristics of a wound-rotor motor are defined by _____. -
Answer- rotor resistance
A three-phase synchronous motor is started with a(n) _____. - Answer- amortisseur
winding
The speed of an induction motor depends on the power supply frequency and the
___. - Answer- numbers of poles
The speed on a multiple-winding motor is normally changed by ____. - Answer-
switching contacts in the motor controller
A consequent-pole motor has _____. - Answer- two speeds
The method of braking in which DC is applied to the motor windings after AC is
removed is known as ____. - Answer- injection braking
Reconnecting a running motor to act as a generator is known as ____. - Answer-
dynamic braking
An insulation resistance test can be used to determine _____. - Answer- whether a
motor is damp
A motor with the field coils connected in parallel with the rotor winding is a _____. -
Answer- shunt motor
The type of motor most likely to be used in a location with flammable dust and torque
fluctuations is a ____. - Answer- squirrel cage induction motor
A type of motor used in precision applications that require constant speed with zero
slip is a _____. - Answer- synchronous motor
Motors: Theory and Application
How DC motors operate? - Answer- Magnetic lines of force are continuous and
always form closed loops; Magnetic lines of force do not cross.
Armature - Answer- The rotating windings of a DC motor.
Commutator - Answer- A device used on electric motors or generators to maintain a
unidirectional current.
Torque - Answer- _____ is produced by mounting a loop in a fixed magnetic field
and as long as the fields of the magnet and armature interact.
horsepower - 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.
magnetic field - Answer- A _____ is produced by the fields poles, and a loop of wire
in the armature turns and cuts this magnetic field.
Horsepower: (Equation) - Answer- Watts/746
Types of DC motors - Answer- Shunt
Series
Compound
Types of AC motors - Answer- Synchronous and Induction (Single and Polyphase)
Periodic duty: (Definition) - Answer- Intermittent operation at a substantially constant
load for a short and definitely specified time.
Revolutions per minute (rpm) - 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.
Rotation - 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.
Synchronous speed - 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.
Field poles - Answer- The stationary portion of a DC motor that produces the
magnetic field.
, The principle reason for developing the brushless DC motor was to ___. - Answer-
eliminate commutator problems
The electrical energy required to produce 1hp of mechanical energy is _____. -
Answer- 746W
When there is a wide variation in both torque and speed requirements, such as a
blower or hoist, use a _____. - Answer- series DC motor
The name of the stationary motor part that produces the magnetic field during
operation is the ____. - Answer- stator
The rpm of a 60Hz motor with two poles is ___. - Answer- 3,600rpm
In three-phase motors, the rotor most commonly used is the _____. - Answer-
squirrel cage rotor
The starting torque characteristics of a wound-rotor motor are defined by _____. -
Answer- rotor resistance
A three-phase synchronous motor is started with a(n) _____. - Answer- amortisseur
winding
The speed of an induction motor depends on the power supply frequency and the
___. - Answer- numbers of poles
The speed on a multiple-winding motor is normally changed by ____. - Answer-
switching contacts in the motor controller
A consequent-pole motor has _____. - Answer- two speeds
The method of braking in which DC is applied to the motor windings after AC is
removed is known as ____. - Answer- injection braking
Reconnecting a running motor to act as a generator is known as ____. - Answer-
dynamic braking
An insulation resistance test can be used to determine _____. - Answer- whether a
motor is damp
A motor with the field coils connected in parallel with the rotor winding is a _____. -
Answer- shunt motor
The type of motor most likely to be used in a location with flammable dust and torque
fluctuations is a ____. - Answer- squirrel cage induction motor
A type of motor used in precision applications that require constant speed with zero
slip is a _____. - Answer- synchronous motor
