Deck 18: Single-Phase Motors

Question 1

When stepping motors are used as two-phase synchronous motors, they can start, stop, or reverse direction of rotation virtually instantly. The motor will start within about 1-1/2 cycles of the applied voltage and will stop within 5-25 ms.

Answer 1

True

Question 2

Multispeed fan motors have been used for many years and are generally wound for ____ steps of speed and operate fans and squirrel-cage blowers.

A) two
B) two to five
C) three
D) four to six

Answer 2

B

Question 3

Motors that are not hermetically sealed use a ____ switch to disconnect the start windings from the circuit.

A) hermetic
B) rotation
C) centrifugal
D) magnetic

Answer 3

C

Question 4

Although a capacitor-start induction-run motor has a high starting torque, the motor should not be started more than two times per hour.

Question 5

In a capacitor-start capacitor-run motor, a capacitor is connected in series with the winding to provide a continuous leading current in the start winding.

Question 6

The speed of a shaded-pole induction motor is determined by the same factors that determine the synchronous speed of other induction motors-____ and number of stator poles.

A) direction of rotation
B) size
C) frequency
D) age

Question 7

In a split-phase motor, synchronous speed is determined by the same two factors that determined the synchronous speed for a three-phase motor: number of stator poles per phase and frequency of the applied voltage.

Question 8

Single-phase ____ motors operate on the principle of a rotating magnetic field developed by a shaded-pole stator. Although they will operate at synchronous speed, they do not require DC excitation current.

A) synchronous
B) consequent
C) shaded-pole
D) shaded-coil

Question 9

A two-phase system is produced by having an alternator with two sets of coils wound 180 degrees apart.

Question 10

The direction of rotation for a split-phase motor is determined by the direction of rotation of the magnetic field created by the run and start windings when the motor ____.

A) is idling
B) has been running for at least five minutes
C) is turned off
D) is first started

Question 11

The stator of a split-phase motor contains two separate windings, the start winding and the ____ winding.

A) end
B) run
C) middle
D) fixed

Question 12

A Warren motor is constructed with a laminated stator core and two coils, which are generally wound for 120 V AC operation.

Question 13

A brush-lifting motor uses a radial commutator, and weights are mounted at the front of the armature. When the motor reaches about ____% of full speed, these weights swing outward due to centrifugal force and cause two push rods to act against a spring barrel and short-circuiting necklace.

A) 50
B) 60
C) 75
D) 90

Question 14

A consequent pole motor is used where high running torque must be maintained at one constant speed.

Question 15

There are three basic repulsion motors: repulsion motor, repulsion-start ____ motor, and repulsion-induction motor.

A) induction-fed
B) induction-run
C) induction-free
D) coil-run

Question 16

A shaded-pole induction motor is popular because of its simplicity and long life.

Question 17

A repulsion-start induction-run motor starts as a repulsion motor but runs as a squirrel-cage motor.

Question 18

Stepping motors are devices that convert ____ into mechanical movement.

A) kinetic energy
B) chemical energy
C) heat
D) electrical impulses

Question 19

Although a repulsion motor does not operate on the principle of a rotating magnetic field, it is an induction motor. When AC power is connected to the stator winding, a magnetic field with alternating polarities is produced in the poles.

Question 20

Many split-phase motors are designed for operation on ____.

A) 120 V only
B) 110 or 220 V
C) 240 V only
D) 120 or 240 V