Master the Basics: NCCER Electrical Level 1 - Module 2 (Introduction to Electrical Circuits)

Master the Basics: NCCER Electrical Level 1 - Module 2
(Introduction to Electrical Circuits)

How DC motors operate? - CORRECT ANSWERS > > Magnetic lines of force are
continuous and always form closed loops; Magnetic lines of force do not cross.

Armature: (Definition) - CORRECT ANSWERS > > The rotating windings of a DC
motor.

The ____ is a movable electromagnet located between the poles of another fixed
permanent (field) magnet as shown. - CORRECT ANSWERS > > Armature

A twisting force called ______ must be developed. _____ is produced by mounting a
loop in a fixed magnetic field and as long as the fields of the magnet and armature
interact. - CORRECT ANSWERS > > Torque

Commentator: (Definition) - CORRECT ANSWERS > > A device used on electric
motors or generators to maintain a unidirectional current.

In the neutral plane, no ____ is produced and the rotation of the armature should stop -
CORRECT ANSWERS > > Torque

A _____ is produced by the fields poles, and a loop of wire in the armature turns and
cuts this magnetic field. - CORRECT ANSWERS > > Magnetic field

CEMF - CORRECT ANSWERS > > Counter electromotive force (CEMF)

Horsepower: (Definition) - CORRECT ANSWERS > > 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.

Horsepower: (Equation) - CORRECT ANSWERS > > Hp= Watts/746

Types of DC motors - CORRECT ANSWERS > > Shunt
Series
Compound

Types of AC motors - CORRECT ANSWERS > > Synchronous and Induction (Single
and Polyphase)

Periodic duty: (Definition) - CORRECT ANSWERS > > Intermittent operation at a
substantially constant load for a short and definitely specified time.

, Revolutions per minute (rpm): (Definition) - CORRECT ANSWERS > > 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: (Definition) - CORRECT ANSWERS > > 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: (Definition) - CORRECT ANSWERS > > 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: (Definition) - CORRECT ANSWERS > > The stationary portion of a DC
motor that produces the magnetic field.

The name of the motor part that rotates during operation is the ____. - CORRECT
ANSWERS > > Armature

The principle reason for developing the brushless DC motor was to ___. - CORRECT
ANSWERS > > eliminate commutator problems

The electrical energy required to produce 1hp of mechanical energy is _____. -
CORRECT ANSWERS > > 746W

When there is a wide variation in both torque and speed requirements, such as a blower
or hoist, use a _____. - CORRECT ANSWERS > > series DC motor

The name of the stationary motor part that produces the magnetic field during operation
is the ____. - CORRECT ANSWERS > > stator

The rpm of a 60Hz motor with two poles is ___. - CORRECT ANSWERS > > 3,600rpm

In three-phase motors, the rotor most commonly used is the _____. - CORRECT
ANSWERS > > squirrel cage rotor

The starting torque characteristics of a wound-rotor motor are defined by _____. -
CORRECT ANSWERS > > rotor resistance

A three-phase synchronous motor is started with a(n) _____. - CORRECT ANSWERS >
> amortisseur winding

The speed of an induction motor depends on the power supply frequency and the ___. -
CORRECT ANSWERS > > numbers of poles