Motor Control

Question 1

What factors need to be considered when installing electrical motors and equipment?

Answer 1

1. Power source
2. Motor connections
3. Motor type
4. Controller type
5. Environment
6. Codes and standards

Question 2

Motor information, such as horsepower, service factor (SF), marked temperature rise, voltage, full-load current rating, and National Electrical Manufacturers Association (NEMA) Code letter, can be found where?

Answer 2

On the motor nameplate

Question 3

Motor control systems can be divided into three major types. Name the 3 types and describe their differences

Answer 3

Manual, semiautomatic, and automatic

Question 4

________ and ________ are methods employed to move a motor with short jabs of power

Answer 4

Jogging and inching

Question 5

Describe the difference between ‘jogging’ and ‘inching’

Answer 5

Jogging is performed by momentarily connecting the motor to full line voltage, while inching is performed by momentarily connecting the motor to reduced voltage

Question 6

________ are voltage-sensitive resistors that have the ability to change their resistance value in accord with the amount of voltage applied to them

Answer 6

Metal oxide varistors (MOV)

Question 7

________ are characterized by the fact that the operator must to the location of the starter to initiate any change of action

Answer 7

Manual starters

Question 8

What is the difference between ‘low-voltage release’ and ‘low-voltage protection’?

Answer 8

Starters equipped with low-voltage release automatically restart when power is restored, while starters equipped with low-voltage protection must be manually reset

Question 9

Overloads are generally set to trip at ________ of motor full-load current

Answer 9

115% - 125%

Question 10

Motor starting current is referred to as ________

Answer 10

Inrush current, or locked-rotor current

Question 11

________ switches are drawn with the movable contact below and not touching the stationary contact

Answer 11

Normally open

Question 12

________ switches are drawn with the movable contact above and touching the stationary contact

Answer 12

Normally closed

Question 13

The rated or nameplate current of a motor is known as ________

Answer 13

Full-load amps (FLA)

Question 14

Another term for across-the-line starting is known as ________

Answer 14

Full-voltage start

Question 15

A magnetic starter and fused safety switch within the same enclosure is called a ________

Answer 15

Combination starter

Question 16

The device in a magnetic starter which helps reduce contact chatter is called a ________

Answer 16

Shading coil

Question 17

The ________ prevents automatic restarting after a power failure

Answer 17

Seal-in contact