Quiz 19

If the 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

LRA

Define a pilot-duty relay.

Low voltage light duty relay

which of the following overload devices is not affected by ambient temperatures

Magnetic

Standards for motor overload protection are set by the ______.

National Electrical code

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

Silver codium oxide

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 the contactors can only have normally open contacts. Which of the following statements is correct?

Technician "A" is correct. Technician "B" is incorrect

An inherent motor protector is a _____.

Thermally activated device in the motor winding

T/F: Auxiliary contacts are usually rated at lower amperage than the contactor's primary contacts.

True

T/F: Bimetal and solder pot overload devices are thermally operated.

True

T/F: Contactor contacts that are badly pitted can cause the motor to burn out.

True

T/F: Magnetic overload devices are the most accurate type of device for electrical protection?

True

T/F: 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.

True

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

Zero ohms

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

cause local heat and may cause it to open up a circuit to the motor

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

components/parts

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

exposes the base metals

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

help obtain equal contacts against the stationary contacts

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

motors reserve capacity

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

provide off-cycle heat to the compressor

The best way to repair a defective relay is by _______

replacing it

Why do many starters have manual resets?

so the technician can reset it by hand

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

to much current or amperage

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

to protect the motor from overheating and damaging itself. Also for quick response to excessive heat on the motor

T/F: A set of contacts are closed when the relays is energized. These contacts are classified as normally closed

False

T/F: A sure sign of contact failure is discoloration on the contact surfaces.

False

T/F: The sun shinning on the a distribution panel has no effect on the breakers in the panel.

False

Define a motor starter.

Has a motor overload protection built into its framework

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

15

Define a contactor.

A bigger relay. A contactor can be repaired and reconstructed

Define a relay.

A electromagnetic switch that can't be replaced or reconstructed