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Single-Phase, Three-phase, Circuit Protection > Powerpoint - Electric Motors > Flashcards

Powerpoint - Electric Motors Flashcards

1
Q

In Hvac, electric motors are used to turn fans, _____ and ________

A

fans, pumps, and compressors

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2
Q

Name 5 pets of an electric motor;

A
  1. stator with windings
  2. rotor
  3. bearings (ball or sleeve)
  4. end bells
  5. housing
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3
Q

Ball bearings are lubricated by ______

A

grease

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4
Q

Sleeve bearings are lubricated by ____

A

oil

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5
Q

Electric motors frames are vented or totally _______

A

enclosed

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6
Q

Electricity and _______ are used to create a motors rotation

A

magnetism

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7
Q

Unlike poles of magnets _______

Like poles of magnets _______

A

attract

repel

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8
Q

The stator has insulated wire windings called ______ and _______ (auxiliary windings)

A

starting and running

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9
Q

The start winding enables the motor to start, it ensures the rotor starts and turns in the proper direction. They are wound with a ______ wire, it is _______ from the cct after is starts

A

smaller, removed

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10
Q

Start windings are closer to the ______ of the motor and run windings are closer to the _______

A

inside, outside

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11
Q

Start capacitors are used to increase starting torque 300- _____%

A

500%

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12
Q

Start capacitors have high capacitance at 75-____MFD

A

75-600MFD

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13
Q

Start capacitors are _________ duty only and never apply voltage exceeding ____% of rating

A

intermittent duty and 130%

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14
Q

Start capacitors voltage rating replacements should never be lower than oem and replacement capacitor must have a capacitance of within ___%

A

20%

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15
Q

Run capacitors are used to improve power factor and reduce current, lower capacitance at 2-___ MFD

A

2-60MFD

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16
Q

Run capacitors are ________ duty and voltage should not exceed ____% of rating, capacitance should be within 5%

A

continuous duty, 110%

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17
Q

CSCR - Capacitor start capacitor run motor:

Start and run capacitor are wired in ________, run capacitor stays in circuit as long as motor is running

A

parallel

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18
Q

Motor slip is the difference between a motors _________ speed and actual running speed, the difference in speed is caused by the _____

A

synchronous, load

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19
Q

Motors should operate within ___% of its rated voltage

A

10%

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20
Q

low voltage will cause the motor to draw high ______ and cause the motor to overheat

A

current

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21
Q

high voltage can cause hot spots within the motor, may cause a decrease in motor _____

A

current

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22
Q

Full load amperage (FLA) is also called rated load amperage (RLA), and it is the current draw while operating at full load conditions and rated ______

A

voltage

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23
Q

The RLA or FLA is approximately 1/5 to ____ of the locked rotor amperage (LRA)

A

1/5 to 1/6

24
Q

Locked rotor amperage is approx 5-__ times higher than the RLA

A

5-6 times

25
Q

Service factor is defined as reserve ___

A

hp

26
Q

Service factor is the range a motor can safely operate past its 100% level for short period of ____

A

time

27
Q

Frequency is the number of _____ per second

A

cycles

28
Q

Canada and US operate at a frequency of ___ hz

A

60

29
Q

Most other countries operate at frequency’s of ___hz

A

50

30
Q

Split phase motors have two separate motor ______ and a medium amount of starting torque.

RPM ranges from 1800-_____

A

windings

1800-3600RPM

31
Q

Centrifugal switches are used commonly on open motors to disconnect the ______ winding

A

start

32
Q

The centrifugal switch disconnects the start winding when the motor reaches 75% of its _____

A

speed

33
Q

Capacitor start motor has a _____ starting torque, start cap is wired in ______ with the start winding and is removed from the cct after _____

A

higher, series, start

34
Q

CSCR is the most efficient _____- phase motor used

A

single phase

35
Q

CSCR are normally used with belt driven _____

A

fans

36
Q

Potential relays are used on motors requiring ____ starting torque

A

high

37
Q

Potential relays have two components; name them

A

coil and contacts

38
Q

potential relay coils have ____ resistance (10,000 to 40,000ohms)
and are wired between terminals __ and __

A

high, 2 and 5

39
Q

Potential relays contacts are normally _____ and are connected between terminals __ and ___

A

closes, 1 and 2

40
Q

CSIR - Capacitor start Induction Run:

Line power makes potential relay open and creates a magnetic field which powers the start winding and keeps the potential relay open so power does not go back to power _____

A

supply

41
Q

Potential relays operated on induces voltage across the _____ winding

A

start winding

42
Q

In a potential relay, the normally closes contact opens when the BEFM rises to specific line voltage, then the start capacitor is _______ and now motor operates as a PSC motor

A

removed

43
Q

Current relays are used on _____ compressors

A

small

44
Q

Current relays are used on single phase, _______ hp motors

A

fractional

45
Q

RSIR- Resistance start Induction run:

high LRA current in current relay coil closes the current relay contact and powers the _____ winding

A

start winding

46
Q

Electronic Relay is used to disconnect the _____ winding, it is a solid state motor starting _____, normally PTC (positive temp coefficient), that means when temp goes up so does _______

A

start, device, resistance

47
Q

PSC motor is the simplest ____-phase motor

A

split phase

48
Q

PSC run capacitor is connected across the start and run terminals and the starting torque is ___

A

low

49
Q

PSC motors can be single speed or multi speed and can be adjusted by swapping motor _____

A

leads

50
Q

Shaded pole motor:

___ starting torque, not as efficient as ____ motor, small shaded pole (starting windings) at corner of each ____, manufactured in the fractional hp range, provides induced current by creating phase shift in ______ field

A

low, PSC, pole, magnetic field

51
Q

Single-Phase Hermetic Motors:

have start and run windings, uses ____ to remove start windings from cct, does not use centrifugal ____, will have run cap to improve _______, designed to operate in ________ atmosphere, common terminal is connected to both the start and run _______

A

relays, switch, efficiency, windings

52
Q

Two speed compressor motors:

speed operation by wiring compressor motor to operate as a 2pole motor or __pole motor, are used to control ______ required by small compressor, considered as two motors in one ______, one turns at 1800 and the other at 3600RPM, have more than 3 motor terminals

A

2 or 4 pole, capacity, housing, 1800 and 3600rpm

53
Q

Special Application Motors:

some single speed motors have more than __ motor terminals, some manufactures design an auxiliary winding in the compressor to give the motor more _______

A

3, efficiency

54
Q

Variable speed motors:

Controlling motor speed gives better ________, decreasing motor speed during low conditions increases ________, voltage and frequency of power supply determines motor _____

A

efficiency, efficiency, speed

55
Q

Cooling Electric Motors:

All motors must be cooled due to heat from electrical _____, hermetic motors are cooled with ________ mainly, open motors are cooled by the _____, some very large motors are cooled by ______

A

energy, refrigerant, air , water

Single-Phase, Three-phase, Circuit Protection (6 decks)

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