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Unit 17 > Unit 17 Quiz > Flashcards

Unit 17 Quiz Flashcards

1
Q

A single-phase dual-voltage motor can be wired for 115V or 230V. When wired for 115V, the run windings are wired in ______ by the technician at the motor terminal box. If the motor is wired for 230V, the run windings are wired in ______.

A

Parallel
Series

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2
Q

The centrifugal switch is used to disconnect the start winding from the circuit when the motor reaches _____% of the rated speed.

A

75%

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3
Q

The difference between the calculated and actual speed of a motor is refereed to as motor ________.

A

Slip

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4
Q

On most shaded pole motors to reverse the direction of rotation, disassemble the motor and turn the _________ over.

A

Stator

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5
Q

The contacts in a potential relay are _______.

A

Normally closed

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6
Q

True or false: Three phase motors do not require a start or run capacitor.

A

True

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7
Q

True or false: A permanent split capacitor motor (PSC) has a start capacitor.

A

False

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8
Q

True or false: Torque is the twisting power of the motor shaft.

A

True

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9
Q

True or false: Voltage leads current in a capacitive circuit.

A

False

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10
Q

True or false: A PSC motor uses only a start capacitor.

A

False

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11
Q

True or false: Reversing a 3-phase fan motor will not affect the air flow.

A

False

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12
Q

True or false: The current magnetic relay has a set of normally closed contacts.

A

False

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13
Q

True or false: in a split phase motor, the start winding is taken out of the circuit to prevent the winding from overheating.

A

True

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14
Q

Capacitor start motors are often referred to as _________.

A

CSIR

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15
Q

The amount by which the current leads or lags voltage is the ______ angle.

A

Phase

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16
Q

The current magnetic relay terminals (CMR) are labeled/marked _______.

A

L,M,S

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17
Q

What energizes the coil in a potential relay to open the contact to take the start capacitor out of the circuit?

A

Electromotive Force

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18
Q

How do you switch the direction of rotation for a three-phase motor?

A

Switch the wiring position of anything 2 lines with each other

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19
Q

You are checking the coils on a potential relay and a current magnetic relay. Which relay has the higher resistance reading?

A

Potential Relay

20
Q

In a CSCR motor, the start and run capacitors are wired in ______ with the start winding but are ______ to one another.

A

Series
Parallel

21
Q

How does a split-phase motor differ from a permanent split capacitor (PSC) motor?

A

-PSC has a run capacitor
-Split may or may not have a run capacitor.

22
Q

What terminals would you place your test probes on to see if the switch is open or closed on a current magnetic relay (CMR)?

A

LMS L&M = Coil. L&S for switch

23
Q

Voltage at which contacts return to their original closed position.

A

Drop out voltage

24
Q

Assists in starting the motor. Uses BEMF to cut out the start capacitor.

A

Potential relay

25
Q

Rotor constructed of bars.

A

Squirrel cage rotor

26
Q

Used to disconnect the start winding from the circuit when motor reaches 75% of the rated speed.

A

Centrifugal switch

27
Q

Resistance to rotation

A

Slip

28
Q

When contacts between terminals 1 & 2 of a potential relay will be opened.

A

Pick up voltage

29
Q

Allows low friction rotation of the rotor. Reduces friction and heat generated by the motor’s moving and rubbing parts and surfaces.

A

Bearings

30
Q

Voltage generated across the start winding by the motor’s rotor when it is up to about 3/4 speed.

A

Back Electromotive Force (BEMF)

31
Q

Can be powered by 115V, 208V, or 230V. Rotation of the motor can be reversed by changing the connections in the motor terminal box.

A

Single phase induction motor

32
Q

Similar to a split phase motor but does not have a start capacitor.

A

PSC motor

33
Q

The diagram below is what type of motor?

A

Multispeed PSC

34
Q

When hooking up the power wires to a three-phase motor, the correct color wire for L1 in the United States, according to the National Electrical Code (NEC) is _______.

A

Black

35
Q

What happens when a capacitor with too much capacitance is used on a PSC motor?

A

May overheat/overload

36
Q

When hoking up the power wires to a three-phase motor, the correct color wire for L3 in the United States, according to the National Electrical Code (NEC) is _____.

A

Blue

37
Q

Calculate the speed of a 6 pole motor operating on 60 Hz.

A
38
Q

When hooking up the power wires to a three-phase motor, the correct color wire for L2 in the United States, according to the National Electrical Code (NEC) is _____.

A

Red

39
Q

How do you determine the direction of rotation for a single-phase and three-phase powered motor?

A

By orientation of the DataPlate. When facing the DataPlate, motor rotation is designated from this point of view unless data plate specifies direction of rotation.

40
Q

What color is the neutral wire when used in a three-phase power supply?

A

White/Grey

41
Q

**EXTRA CREDIT
1. you are getting power to the thermostat. You switch the thermostat to “Cool”, but nothing happens after the 5-minute delay. What are some things you can do to confirm the thermostat is broken?

A

Wire all lines together to see what activates. If something doesn’t activate, it’s broken somewhere.

42
Q

EXTRA CREDIT
2. A step-up transformer has more windings in the ______ than the _____.

A

Secondary
Primary

43
Q

EXTRA CREDIT
3. A motor uses a start and run capacitor. The start capacitor is rated at 45 uf and the run capacitor is rated at 5 uf. What is the total capacitance in the circuit when the motor is starting?

A

50 uf

44
Q

EXTRA CREDIT
4. The switch in a potential relay is between terminals ____and____ while the switch in a current magnetic relay is between terminals ___ and ____.

A

2 & 1
L & S

45
Q

EXTRA CREDIT
5. A motor that uses ball bearings may make too much noise that could be transferred through metal duct work. A motor using what type of bearings would be preferred?

A

Sleeve Bearings

Unit 17 (2 decks)

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