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Flashcards in Notes Deck (36)
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1
Q

What happens with current in AC motors?

A

large inrush currents when they start up and then current falls to rated values

2
Q

As mechanical load increases the _________ will also increase?

A

current

3
Q

Toggle switch and knife switch rating?

A

max rating is 1hp @230v

4
Q

What does a toggle switch prevent and what is it sometimes called?

A

arcing

snap-action switch

5
Q

Main difference between a regular switch and motor switch?

A

motor switch must be hp rated

6
Q

T/F? Hp rating of a starter must meet or exceed the hp of the motor?

A

True

7
Q

how is the starter connected with the supply line and motor terminals?

A

in series

8
Q

Push button starter rating?

A

max 5hp @230v

9
Q

Difference between push button starter and toggle switches?

A

push button starter uses two separate buttons to activate contacts

10
Q

Drum-switch rating?

A

max 3hp @240v or 1.5hp @120v

11
Q

What is a drum switch?

A

rotary action selector switch

12
Q

what is a drum-switch used for?

A

used to control speed (no overload protection)

13
Q

Does an isolating switch need to be hp rated?

A

No

14
Q

What does an isolating switch do?

A

isolates machine without interrupting power source

15
Q

Two most common overload relays?

A

melting-alloy

bi-metallic strips

16
Q

What is thermal overload protection?

A

guards against mechanical overloading or high voltages

17
Q

What is a melting-alloy overload relay often referred to as?

A

solder pot

18
Q

what does a bi-metallic strip have?

A

a bi-metallic strip close to the heater element

19
Q

What must you do when an overload occurs?

A

wait until it cools down before you reset it

20
Q

Overload with toggle switch?

A

will move to center and must be switched off before turning back on

21
Q

Overloading with push button types?

A

Button will extend fully and must be pushed in before pushing on

22
Q

what does low voltage release mean?

A

motor will automatically restart when power returns

23
Q

Overload definition?

A

a current greater than normal inside path (protected by OL relay)

24
Q

Overcurrent definition?

A

A greater current than normal outside normal path (protected by the line fuses)

25
Q

how many lines does single, double pole and three pole interrupt?

A

1
2
3

26
Q

How are Stop Push buttons connected?

A

Series

27
Q

How are Start Push buttons connected?

A

Parallel

28
Q

What is located in the magnetic starter?

A

Seal in contacts, coil, and auxiliary overloads

29
Q

Difference between two-wire and three-wire circuit?

A

Two-wire (low voltage release)

Three-wire (low voltage protection)

30
Q

What are control relays used for?

A

used as auxiliary contacts to control low current coils of the magnetic starter

31
Q

Hand off auto selector switch?

A

used for manual and automatic controls

32
Q

What are control relays used for?

A

Lights, alarms, small motors, or electric heaters

33
Q

What are control relays also known as?

A

poles

34
Q

What are contacts usually rated at?

A

10amps , as high as 600v AC

35
Q

Name the three different current ratings?

A

Inrush or make contact ratings

Normal or continuous rating

Opening or break contact rating

36
Q

why are jogging circuits dangerous?

A

there is a chance of the contacts staying closed