Deck 5: Relays, Contactors, and Motor Starters

Question 1

The advantage of mercury relays is that each time the relay is used the contact is renewed, eliminating burning and pitting caused by an arc when connection is made or broken.

Answer 1

True

Question 2

What are coil clearing contacts?

Answer 2

Many latching type relays and contactors contain contacts that are used to prevent continuous power being supplied to the coil after it has been energized. These contacts are generally called coil clearing contacts.

Question 3

Mechanically held contactors and relays are often referred to as ____________________ contactors or relays.

Answer 3

latching

Question 4

What are relays?

Question 5

The continuous change of both amplitude and polarity of the magnetic field causes currents to be induced into the metal core material; these currents are called ____________________ currents.

Question 6

All solenoids that operate on alternating current must have a(n) ____________________ coil.

Question 7

Hysteresis loss is often referred to as molecular friction.

Question 8

What is a reason for sealing load contacts inside a vacuum chamber?

Question 9

Why is it that bridge contacts can control more voltage than clapper types?

Question 10

Vacuum contactors enclose their load contacts in a sealed vacuum chamber.

Question 11

Motor starters are basically a contactor and overload relay mounted together. Most do not need auxiliary contacts.

Question 12

Auxiliary contacts are intended to control large amounts of current.

Question 13

Relays and contactors operate on the ____________________ principle.

Question 14

Contactors are equipped with contacts intended to connect high current loads to the power line; these large contacts are called ____________________ contacts.

Question 15

How is optoisolation achieved?