Deck 5: Relays, Contactors, and Motor Starters

Question 1

What are relays?

Answer 1

Relays are electromechanical switches that contain auxiliary contacts.

Question 2

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

Answer 2

Sealing contacts inside a vacuum chamber permits them to switch higher voltages with a relative narrow space between the contacts without establishing an arc.

Question 3

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

Answer 3

latching

Question 4

What are coil clearing contacts?

Question 5

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

Question 6

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 7

Auxiliary contacts are intended to control large amounts of current.

Question 8

Hysteresis loss is often referred to as molecular friction.

Question 9

How is optoisolation achieved?

Question 10

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

Question 11

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

Question 12

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

Question 13

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

Question 14

Relays and contactors operate on the ____________________ principle.

Question 15

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