Deck 19: Motor Controls

Question 1

A common practice in condensing units is to use a contactor with only one set of contacts opening only one side of the power to the unit. This is to ____.

A) reduce the cost of the contactor
B) make it easier to wire the unit
C) teach the service technician not to put hands in the unit with the power on
D) provide off-cycle heat to the compressor

Answer 1

D

Question 2

Bimetal and solder pot overload devices are thermally operated.

Answer 2

True

Question 3

A sure sign of contact failure is discoloration on the contact surfaces.

Answer 3

False

Question 4

The best way to repair a defective relay is by ____________________.

Question 5

When a contactor's coil is energized, how much resistance should be measured between terminal "L1" and terminal "T1"?

A) zero ohms
B) 50-3000 ohms
C) 5000-6000 ohms
D) infinite

Question 6

Beside maintaining pressure on the contacts for current carrying capacity, the pressure springs have a second important function. This is to ____.

A) keep the contacts in line
B) help obtain equal contacts against the stationary contacts
C) slow down the pull of the armature into place to reduce the noise
D) increase the power required to close the contacts

Question 7

Which of the following overload devices is not affected by ambient temperature?

A) solder pot
B) magnetic
C) bimetal
D) time-delay fuse

Question 8

An inherent motor protector is a ____.

A) circuit breaker
B) motor starter overload
C) thermally activated device in the motor winding
D) line fuse

Question 9

The most common material used on the surface of contacts is ____________________.

Question 10

A solder pot is part of a ____.

A) one-time fuse
B) resettable circuit breaker
C) time-delay fuse
D) plumber's tool kit

Question 11

A set of contacts are closed when the relay is energized. These contacts are classified as normally closed.

Question 12

Contactor contacts that are badly pitted can cause the motor to burn out.

Question 13

The locked rotor amperage, LRA, of a motor is typically five times higher than the full load amperage, FLA, of the motor and can be as high as seven times the FLA.

Question 14

The service factor of an electric motor is determined by ____.

A) National Electrical Code
B) National Electrical Manufacturers Association code
C) motor's reserve capacity
D) the required wire size supplying power to the motor

Question 15

Magnetic overload devices are the most accurate type of device for electrical protection.

Question 16

Standards for motor overload protection are set by the ____.

A) United States Department of Transportation
B) National Electrical Code
C) Environmental Protection Agency
D) American National Standards Institute

Question 17

Auxiliary contacts are usually rated at a lower amperage than the contactor's primary contacts.

Question 18

If a normally operating motor draws 75 amps on startup, it will most likely draw ____________________ amps when running.

Question 19

Technician "A" says that if you take a voltage reading from terminal "L1" to terminal "T1" on a contactor whose coil is energized, you should read zero volts. Technician "B" says that contactors can only have normally open contacts. Which of the following statements is correct?

A) Technician "A" is correct. Technician "B" is correct.
B) Technician "A" is correct. Technician "B" is incorrect.
C) Technician "A" is incorrect. Technician "B" is correct.
D) Technician "A" is incorrect. Technician "B" is incorrect.

Question 20

The sun shining on a distribution panel has no effect on the breakers in the panel.

Question 21

Why do many starters have manual resets?

Question 22

Define a contactor.

Question 23

The best way to repair a large contactor is by the replacement of ____________________.

Question 24

Define a motor starter.

Question 25

Why should a technician not file the rough surfaces of a contactor's contacts?

Question 26

What effect would a loose connection have on a solder pot overload device?

Question 27

What causes the overload of a starter to open and disable the power circuit?

Question 28

Define a relay.

Question 29

Define a pilot-duty relay.

Question 30

If a relay starts the indoor fan in the cooling mode of a central air-conditioning system, it must be able to withstand the ____________________  of the fan motor on start-up.

Question 31

Why is a starter equipped with overload protection when the circuit already has a fuse or circuit breaker?