AC Motor Quiz

Question 1

What are the two types of motors?

Answer 1

AC and DC

Question 2

What are the voltage ranges for single phase AC motors?

Answer 2

110, 115, 120, 220, 230, 240 VAC

Question 3

What are the voltage ranges for three phase AC motors?

Answer 3

208, 220, 230, 240, 480 VAC

Question 4

How is frame information indicated for motors with two #’s?

Answer 4

It’s that into 1/16” of an inch.

Question 5

How is frame information indicated for motors with three #’s?

Answer 5

The first two numbers over 4; the third number tells about the bolt pattern.

Question 6

What do the letters in motor frame information indicate?

Answer 6

• T = Long Shaft
• TS = Short Shaft
• C = C-Face Motor
• TC = Long Shaft C-Face
• JM, JP = Close Coupled

Question 7

What are some reasons for AC motor overheating?

Answer 7

• High or Low Voltage
• Frequent or Repeated Starts
• High Ambient Temps
• Clogged/Dirty ventilation holes or cooling fans
• Voltage imbalance in 3 Phase Motors

Question 8

What does motor insulation indicate?

Answer 8

Motor Class

Question 9

What are the common motor insulation classes?

Answer 9

• A
• B
• F

Question 10

What does Service Factor (S.F) indicate?

Answer 10

Amount of overload a motor can deliver without overheating.

Question 11

What does a Service Factor of 1.0 represent?

Answer 11

Load rated on nameplate.

Question 12

What does a Service Factor of 1.15 represent?

Answer 12

115% of rated load.

Question 13

What does a Service Factor of 1.25 represent?

Answer 13

125% of rated load.

Question 14

What happens to torque and current when speed is low?

Answer 14

Torque and current are high.

Question 15

What happens to torque and current when speed is high?

Answer 15

Torque and current are low.

Question 16

What is a C-Face motor mounting?

Answer 16

Motor supports Driven unit.

Question 17

What is a D-Flange motor mounting?

Answer 17

Motor is supported by driven unit.

Question 18

What are the overload protection methods for single-phase motors?

Answer 18

• Automatic Thermal Overloads
• Manual Thermal Overloads

Question 19

What are the overload protection methods for three-phase motors?

Answer 19

• Thermostats
• Thermistors
• Resistance Temp Detectors

Question 20

What are the parts of AC motors?

Answer 20

• Stator
• Rotor
• Fan Side End Bracket
• Coupling Side End Bracket
• Fan
• Fan Shroud

Question 21

What does the number of motor poles indicate?

Answer 21

More poles lead to lower RPM and higher torque.

Question 22

What is slip in motors?

Answer 22

The difference between the sync speed and the actual speed (1%-5%).

Question 23

Why are three-phase motors common?

Answer 23

Low cost and high efficiency.

Question 24

What is a major problem with single-phase motors?

Answer 24

Little to no start-up torque available.

Question 25

What type of motor uses a shading ring?

Answer 25

Shaded Pole motor.

Question 26

Where are shaded pole motors typically used?

Answer 26

Small appliances.

Question 27

What characterizes a split-phase motor?

Answer 27

Start windings positioned 90 degrees from run windings, drop out at ¾ of sync speed.

Question 28

What applications are split-phase motors typically used for?

Answer 28

Light duty applications.

Question 29

What is a capacitor-start motor?

Answer 29

Has a capacitor in series with start winding for over 200% more starting torque.

Question 30

What is a common application for capacitor-start motors?

Answer 30

Most common in various applications.

Question 31

What are perm split capacitor motors known for?

Answer 31

Identical main and auxiliary windings with a capacitor, very little starting torque.

Question 32

What applications are perm split capacitor motors used for?

Answer 32

Fans and pumps for HVAC, 1 HP or below.