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ELX > Motor Controll > Flashcards

Motor Controll Flashcards

1
Q

What is the disadvantage of a manual motor starter compared to a magnetic motor starter

A

No low-voltage protection
Only one location available for stopping/starting

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2
Q

Why must a single pull starting switch be connected in the “underground” circuit conductor

A

It will open up the hot to the motor if the contact is open or tripped the motor is at ground potential 

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3
Q

How would you reset a toggle type of manual starter that has tripped due to overload?

A

First turn completely to the off position, and then turn it back to the on position just like a circuit breaker

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4
Q

Describe manual motor control

A

Non-magnetic means push button or toggle switch

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5
Q

Describe automatic motor control

A

Using an electromagnetic starter with all of the controller benefits

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6
Q

What is the difference between overload protection and overcurrent protection?

A

Overload uses OL heat to protect the motor in the case of an overload

Overcurrent protects the whole circuit from grounds and shorts

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7
Q

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

A

LVR=2 wire control motor could reset automatically

LVP = three wire control requires a manual reset

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8
Q

What is a motor that uses low-voltage protection?

A

Lathes in the high school woodshop

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9
Q

What are motors that use low-voltage release?

A

Sump pump, ventilation, fan, air compressor

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10
Q

What is meant by “across the line” starting

A

The motor is connected to the full voltage of the source when starting

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11
Q

What is a combination starter?

A

Connecter with overload heaters, overcurrent, protection, fuse, circuit, breaker, and a disconnect

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12
Q

What does a power circuit have in it

A

(Power circuit) -disconnect, overcurrent protection, horsepower rated contacts, overload heater, motor branch circuit, conductors

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13
Q

What does a control circuit have in it?

A

(Control circuit) - overload contact control relay stop/start limit switches, auxiliary contacts

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14
Q

What is a schematic diagram?

A

Schematic shows the electrical relationships of the components

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15
Q

What is a wiring diagram?

A

It shows the physical location used to construct the circuit and how the connections are made

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16
Q

Why is it necessary for motor starters to be rated in horse power?

A

So they can handle the inrush current that is drawn when the motor is started

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17
Q

What is meant by the term normally closed and normally open

A

(Normally open contact) open in the de-energized state.

(Normally closed contact) - closed in denergized state

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18
Q

Why are magnetic starter? Contacts generally silver

A

Provide a lower resistant path
Doesn’t allow oxide to build up
Keeps contacts cooler

19
Q

What parts of the magnetic starter are in the power circuit

A

Disconnect, overcurrent, device fuse/breaker main contacts, overload heaters, motor branch circuit wiring

20
Q

What parts of the magnetic starter are in the control circuit

A

Overload contacts coil start/stop push button auxiliary contacts holding contacts limit switches

21
Q

Why are some combinations starters provided with a door mechanical interlock?

A

So you cannot open them in the on position

22
Q

What is the difference between a magnetic starter and a magnetic contactor

A

Starter has a connecter plus overload heaters

23
Q

Why would you provide an overload relay to protect a motor circuit if the motor is already protected by a fuse?

A

It protects the motor overload conditions more precisely

24
Q

What are two different types of thermal overload relays?

A

A) Bi-metallic
B) melting alloy/solder pot

25
Q

What part of a thermal overload relay is in the power circuit

A

Heaters

26
Q

What part of a thermal overload relay is in the control circuit

A

Close contact

27
Q

Rather than overload, what conditions might cause the overload to trip?

A

High temperature loose connection, wrong heater selection

28
Q

Why is the automatic reset overload used more then the manual reset type

A

It requires someone to physically check things out before resetting

29
Q

List the events that describe the protection of a thermal over

A

Motor has an overload condition draws too much in power circuit, creating heat and overload heat either melts or bends solder pot/bi metallic strip, which will open the normally closed overload contact

30
Q

State the effects of ambient temperature on a by metallic type of overload

A

If the temperature is too high, the bi metallic strip will be permanently bent

31
Q

What do you have to do if the exact heater is not available for an overload relay?

A

Try to get one that is as close as possible and use a percent adjustment overload relay

32
Q

What is the difference between a start pushbutton and a stop push button

A

Stop— normally closed and connected in series
Start—normally open and connected in parallel

33
Q

How does a start push button actually start motor

A

When the start push button is pressed it energizes the coil, which then turns on the motor Contacts

34
Q

What is two wire control?

A

Low-voltage release if no power it will restart

35
Q

What is three wire control?

A

Low-voltage protection if no power, someone has to restart it

36
Q

What is the seal in contact / holding contact

A

It is used to keep the magnetic starter energize until stopped

37
Q

What is the normally open limit switch?

A

End of process

38
Q

What is a close limit switch?

A

End of travel

39
Q

What is it normally open push button

A

Start botton

40
Q

What is it normally closed push button

A

Stop button

41
Q

What is a Two position selector switch

A

Manually run and off

42
Q

What is a three position selector switch?

A

Hand/off/auto application

43
Q

What is a pilot light?

A

Run/stop overload blown indication

44
Q

What does a holding or seal in contact

A

It keeps the motor running

ELX (55 decks)

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