Chapter 11 - Motors

Question 1

Electric motors operate on the principle that a force acts on a conductor when it carries current in a magnetic field

Answer 1

True

Question 2

AC motors typically direct on AC power lines.

Answer 2

True

Question 3

D-flange motors have clearance holes without threads and can be directly bolted on to machinery.

Answer 3

True

Question 4

AC motors contain two main parts-the stator and the rotor.

Answer 4

True

Question 5

AC motor stators contain windings with two or more magnetic poles per phase.

Answer 5

True

Question 6

AC induction motor rotors consist of a laminated cylinder with plastic bars in slots around the outer part of the cylinder.

Answer 6

False

Question 7

The rotational speed of the stator’s magnetic field is called the synchronous speed of the motor.

Answer 7

True

Question 8

Locked-rotor torque available at zero speed for accelerating the load.

Answer 8

True

Question 9

Polyphase motors are available in ratings from fractional to thousands of horsepower.

Answer 9

True

Question 10

The Canadian equivalent of NEMA is NAFTA.

Answer 10

False

Question 11

The majority of general-purpose, three-phase motors manufactured after October 24, 1997 are required to meet EPACT.

Answer 11

True

Question 12

Inverters or Variable Frequency Drives (VFD) were developed to control the voltage and frequency to DC motors.

Answer 12

False

Question 13

DC motors are less complex and costly than corresponding AC induction motors.

Answer 13

False

Question 14

There are two basic types of DC motors - brush and brushless.

Answer 14

True

Question 15

Three types of wound-field DC motors included series, shunt, and compound wound.

Answer 15

True

Question 16

Motors that are recognized as meeting North American standards for hazardous locations also can be assured to meet IEC standards.

Answer 16

False

Question 17

Another name for a 3-phase motor is

Answer 17

Polyphase motor

Question 18

Motors that operate on 60 Hz power systems are used in

Answer 18

Mexico

Question 19

Doubling motor load:

Answer 19

Raises motor heating four times.

Question 20

Variable-torque loads include

Answer 20

Fans

Question 21

The synchronous speed of a 4 pole, 60 Hz motor is

Answer 21

1800

Question 22

The difference between synchronous and actual rotor speed for a Design B motor is

Answer 22

3-5 percent at full load

Question 23

PM motors are offered in sizes from

Answer 23

1/4 to 5 HP

Question 24

General-purpose brushless DC motors are widely available with ratings up to about

Answer 24

20 HP at 1800 rpm

Question 25

A typical DC motor option is a

Answer 25

Tachometer, Blower, Space heater (All of the above)

Question 26

The majority of general-purpose, three phase motors manufactured after ____ are required to meet EPACT mandates.

Answer 26

1997

Question 27

Locked-rotor torque is torque available at what speed for accelerating the load?

Answer 27

0

Question 28

AC motor stators contain windings with two or more poles per phase. What type of poles are these?

Answer 28

Magnetic

Question 29

What type of motor consists of two basic types including brush and brushless?

Answer 29

DC

Question 30

Brushless motors do not have what?

Answer 30

Both Brushes and Commutators