Deck 18: Single-Phase Motors

Question 1

As the current in the stator circuit increases, the stator ____________________ also increases.

Answer 1

flux

Question 2

In the ____________________ method, an additional compensating winding is placed in slots cut in the pole faces.

Answer 2

conductive compensation

Question 3

Describe a bifilar stepping motor.

Answer 3

The term bifilar means that there are two windings wound together. This is similar to a transformer winding with a center-tap lead. A bifilar stepping motor has twice as many windings as does the three-lead type, which makes it necessary to use smaller wire in the windings. This results in higher wire resistance in the winding, producing a better inductive-resistive (L/R) time constant for the bifilar wound motor. The increased L/R time constant results in better motor performance. The use of a bifilar stepper motor also simplifies the drive circuitry requirements. Notice that the bifilar motor does not require an aboveground-belowground power supply. As a general rule, the power supply voltage should be about five times greater than the motor voltage. A current-limiting resistance is used in the common lead of the motor. This current-limiting resistor also helps improve the L/R time constant.

Question 4

A(n) ____________________ network can be used to provide the 90° phase shift needed to change single-phase ac into two-phase ac.

Question 5

When stepping motors are used as two-phase synchronous motors, they have the ability to virtually start, stop, or reverse direction of rotation instantly.

Question 6

A repulsion-induction motor has nearly the same operating characteristics as a repulsion-start, induction-run motor, but this type of motor has no ____________________ mechanism.

Question 7

Describe stepping motors that are operated on ac voltage.

Question 8

Universal motors operate at different speeds on dc and single-phase ac.

Question 9

The rotor of the resistance-start, induction-run motor is the same as that of a three-phase, squirrel-cage induction motor.

Question 10

Stepping motors are devices that convert mechanical movement into electrical impulses.

Question 11

What are the two main types of single-phase induction motors?

Question 12

What are the basic parts of a resistance-start, induction-run motor?

Question 13

The term ____________________ means that there are two windings wound together.

Question 14

What is the theory of operation for stepping motors?

Question 15

Most single-phase motors have fractional horsepower ratings.