DEL 33

Question 1

To reverse the direction of rotation of a three-phase motor, reverse _____.

Answer 1

any two leads

Question 2

A motor is operating at 3450 RPM and is producing a torque of 32 lb-in. What is the output horsepower of the motor?

Answer 2

1.75 hp

Question 3

Three lines supply power to a three-phase motor. If one of these lines should open, the motor will be connected to single-phase power. This condition is known as _____.

Answer 3

single-phasing

Question 4

The torque of a squirrel-cage induction motor will be maximum when the phase angle between the stator and rotor fields is _____.

Answer 4

0°

Question 5

The squirrel-cage rotor code letters indicate the shape (type) of rotor bars. Different types of bars have a large effect on the _____ of a motor.

Answer 5

starting torque

Question 6

Selsyn motors operate on _____ voltage.

Answer 6

single-phase

Question 7

When a squirrel-cage motor is first started, the value of the current draw is _____.

Answer 7

several times the running current

Question 8

A squirrel-cage rotor induction motor has a synchronous speed of 3600 RPM and an actual rotor speed of 3450 RPM. What is the percent slip?

Answer 8

4.17%

Question 9

The squirrel-cage rotor is constructed of _____ and end _____ embedded in steel laminations.

Answer 9

bars; rings

Question 10

The set of squirrel-cage bars on the rotor of a synchronous motor is used to start the motor and is known as the _____.

Answer 10

amortisseur winding

Question 11

The frequency of the current in a squirrel-cage rotor _____ as the rotor approaches synchronous speed.

Answer 11

decreases

Question 12

For most squirrel-cage induction motors the typical percent slip is about _____ percent.

Answer 12

two to five

Question 13

The wound-rotor induction motor is popular in industry because it has _____ starting torque and _____ starting current.

Answer 13

high; low

Question 14

In a three-phase motor, the speed of rotation of the magnetic field is called the _____ speed.

Answer 14

synchronous

Question 15

Some motors are constructed so that they will operate on either of two voltages. When they are connected to operate on the higher of the two voltages, the windings are connected in _____.

Answer 15

series

Question 16

If a piece of machinery needs a replacement motor and will be damaged if the new motor rotates the wrong way. The test equipment needed to test the rotation direction of the new motor is a _____.

Answer 16

phase rotation meter

Question 17

A synchronous motor operated with no load and used for power factor correction is sometimes called a _____.

Answer 17

synchronous condenser

Question 18

In the consequent pole motor, if the number of poles is doubled, the motor speed will be _____.

Answer 18

cut in half

Question 19

Some motors are constructed so that they will operate on either of two voltages. When they are connected to operate on the lower of the two voltages, the windings are connected in _____.

Answer 19

parallel