Single Motor Control/Pilot Devices and Symbols. Flashcards Preview

Electrical Lab MCSC Period 2 SAIT-Alberta > Single Motor Control/Pilot Devices and Symbols. > Flashcards

Flashcards in Single Motor Control/Pilot Devices and Symbols. Deck (20)
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1

What are the three main sections of a basic stop/start motor control circuit?

Stop circuit.
Start circuit.
Holding circuit.

2

What are the other names of "Holding contacts"?

Seal-in, hold-in, or maintaining contacts.

3

Interlocks placed in the holding circuit affect which functions of the motor starter?

Running the motor,
Stopping the motor.

4

Interlocks placed in the stop circuit affect which functions of the motor starter?

Starting the motor,
Running the motor,
Stopping the motor.

5

Interlocks placed in the start circuit affect which functions of the motor starter?

Starting the motor.

6

When using multiple stop/start stations, how are additional STOP buttons placed?

In series, in the stop circuit.

7

When using multiple stop/start stations, how are additional START buttons placed?

In parallel with the start circuit and holding circuit.

8

What are the terminal numbers of an IEC contactor's holding contacts?

13 & 14.

9

What are the terminal numbers of an NEMA contactor's holding contacts?

2 & 3.

10

If a pilot light is to indicate motor running, where is it placed in the control circuit?

In parallel with the contactor coil.

11

What is the prime difference between low voltage release and low voltage protection?

LVP uses a holding circuit to require a manual reset after a power failure, whereas LVR will automatically restart after power restoration.
It is important to note that LVP requires a manual start method.

12

Is an emergency stop device considered a momentary device?

No.
It uses a latching mechanism so it would be considered, a maintained device.

13

When used as a pilot device, what is a silicon diode generally used for?

Temp sensor in the cryogenic range (

14

Do bimetallic temperature sensing devices require current to operate?

No.
Through the properties of thermal expansion, the dissimilar metals expand at differing rates causing a deflection.

15

What is a typical application of a dual-stage pressure switch?

Alarm stage, followed by a shutdown stage.

16

Could you use a proximity switch to measure liquid level?

Yes.
Some liquid level switches use the same principles as typical proximity switches.

17

What is considered to be the normal position of pilot devices?

The position in the absence of any operating medium.
(no electricity, no liquid, no pressure, etc...).

18

What normal configuration would a "close on rise" pilot device be in?

Normally open.

19

What normal configuration would a "open on rise" pilot device be in?

Normally closed.

20

What should you do when you encounter a symbol that you do not recognize?

Consult the legend.