Deck 5: Relays, Contactors, and Motor Starters

Question 1

How is optoisolation achieved?

Answer 1

Optoisolation is achieved by using the light from a light emitting diode (LED) to energize a photo triac.

Question 2

Relays and contactors that are operated by direct current generally contain laminated cores.

Answer 2

False

Question 3

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

Answer 3

latching

Question 4

Relays and contactors operate on the ____________________ principle.

Question 5

What are coil clearing contacts?

Question 6

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

Question 7

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

Question 8

When the coil of an alternating current relay or contactor is energized, it will require less current to pull the armature in than to hold it in.

Question 9

Hysteresis loss is often referred to as molecular friction.

Question 10

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

Question 11

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

Question 12

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

Question 13

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 14

What are relays?

Question 15

Auxiliary contacts are intended to control large amounts of current.