Deck 12: Two-Wire Motor Control

Question 1

No-voltage drop-out or two-wire control circuit should indicate a possible ____ to the electrician, because a mechanically held closed pilot device could automatically restart the load motor when the power is restored.

A)safety concern
B)power restart
C)magnetic charge
D)controlled condition

Answer 1

A

Question 2

Two-wire motor control circuits are called two-wire because there are only two control circuit wires between the motor starter and the control device(s).

Answer 2

True

Question 3

A pilot device is the term given to any two-wire control circuit component that mechanically closes and opens its control contacts, depending on the state of the medium it is measuring.

Answer 3

True

Question 4

What is the purpose of a hand-off-automatic circuit?

Question 5

The pilot control device shuts down at a loss of power.

Question 6

Two-wire motor control circuits are extremely complex motor control circuits.

Question 7

Differential controls provide a mechanical means, _______________ of the electrical control circuit.

Question 8

A differential control device is a two position (on/off) switch that actuates when the measured medium reaches either of the two pre-determined extreme high or low range values, with a dead zone in between where the switch does not change states.

Question 9

The pilot control device is a(n) _______________ control, which is unaffected by the loss of power.

Question 10

The purpose of a hand-off-automatic circuit is to give the operator three operating modes; a manual hand position, off, and an automatic position where the pilot device automatically controls the control coil.

Question 11

It is extremely uncommon to find differential switches for pilot devices in these motor control circuits.

Question 12

The purpose of a _____-automatic circuit is to give the operator three operating modes; a manual hand position, off, and an automatic position where the pilot device automatically controls the control coil.

A)hand-on
B)hand-off
C)pilot
D)ladder

Question 13

Differential controls provide a mechanical means that acts like a mechanical holding circuit.

Question 14

_______________ motor control circuits only have two control circuit wires between the motor starter and the control device(s).

Question 15

The phrases no-voltage drop-out, or two-wire control circuit should indicate a possible safety concern to the electrician, because a mechanically held closed pilot device could automatically restart the load motor when the power is restored.

Question 16

Describe two-wired motor control circuits.

Question 17

An example of a differential control device is a(n) ______.

A)timer
B)dial
C)regulator
D)on/off switch

Question 18

Pilot devices control the motor starter control coil.

Question 19

Two-wire control components are called ____ devices.

A)mechanical
B)pilot
C)coil
D)starter

Question 20

Two-wire control provides both no-voltage drop-out protection, or low-voltage drop-out protection.