Deck 13: Three-Wire Motor Control

Question 1

What does inhibit and enable contacts mean?

Answer 1

More often than not, when normally closed control contacts under the operation of a coil are used in the ladder rung logic, their purpose is to prevent two operations from happening at the same time.Because of this, normally closed contact devices on ladder rungs are sometimes called inhibit contacts or devices, because the action of one operation inhibits some other operation from acting simultaneously.Likewise, more often than not, when normally open control contacts under the operation of a coil are used in the ladder rung logic, their purpose is to enable some other operation to happen at the same time.Because of this, normally open contact devices on ladder rungs and are sometimes called enable contacts, because the action of one operation enables some other operation to act simultaneously.

Question 2

When control circuit power is first applied to the three-wire motor control circuit, the rails become ____.

A)energized
B)magnetized
C)polarized
D)heated

Answer 2

A

Question 3

The normally closed Stop pushbutton is wired as the third control component in the ladder rung, so that it has master control over the entire rung.

Answer 3

False

Question 4

Normally closed contact devices on ladder rungs are sometimes called "exhibit" contacts or devices.

Question 5

Stop pushbuttons are normally closed contact configurations.Why?

Question 6

Once the motor starter contactor control coil is energized, and being held energized by the holding contacts, pressing the normally closed Stop pushbutton will de-energize the control coil; causing the contactor holding contacts to open.

Question 7

Once the motor starter contactor is energized and closes the holding contacts, the holding contacts provide a redundant electrical path around the normally open Start pushbutton contacts, to keep the contactor control coil energized.

Question 8

Normally open contact devices on ladder rungs and are sometimes called ____ contacts.

A)prohibit
B)extend
C)inhibit
D)enable

Question 9

Permanent contact control devices are called-out as either normally open or normally closed.

Question 10

Normally closed contact devices on ladder rungs are sometimes called ____ contacts or devices.

A)prohibit
B)extend
C)inhibit
D)enable

Question 11

When control devices are connected in parallel, they form the Boolean "_______________" function.

Question 12

The second device in the motor control ladder diagram run is the ____ pushbutton.

A)start
B)stop
C)pause
D)jog

Question 13

Three-wire motor control circuits are called three-wire, because there are three _______________ circuit wires between the motor starter and the control device(s).

Question 14

Three-wire control circuit components may be either maintained contact or momentary contact, but the _______________ contact function is specific to three-wire control.

Question 15

_______________ contacts are a normally-open set of contacts mounted on the contactor portion of the motor starter, and are actuated by the armature of the contactor unit.

Question 16

When the ____ pushbutton is pressed, the control circuit power will pass through to the motor starter contactor control coil S1.

A)start
B)stop
C)pause
D)jog

Question 17

____ contact control devices change states when acted upon, but then return to their original state when released.

A)Standard
B)Momentary
C)Magnetic
D)Pushbutton

Question 18

One of the other names of holding contacts is ____ contacts.

A)mounted
B)variable
C)magnetic
D)memory

Question 19

The ____ pushbutton will always be the first device off of L1, so that it has "master control" of the rung.

A)start
B)stop
C)pause
D)jog

Question 20

Three-wire motor control circuits have three control circuit wires between the motor starter and the control device(s).