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Single-Phase, Three-phase, Circuit Protection > RACT - Unit 17 Review questions > Flashcards

RACT - Unit 17 Review questions Flashcards

1
Q

Two common operating voltages for residential equipment are ______________.

a. 24 V and 230 V 

b. 115 V and 24 V	
c. 230 V and 277 V	
d. 115 V and 230 V
A

115v and 230v

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2
Q

When an open motor gets up to speed, the ___________ switch takes the start winding out of the circuit.

a. rectifier 

b. transistor	
c. centrifugal	
d. inverter
A

centrifugal

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3
Q

In a single-phase motor, the motor windings that have the highest resistance are the __________ windings.

a. run 

b. rotor	
c. shaft	
d. start
A

start

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4
Q

Which of the following devices may be wired into the starting circuit of a motor to improve the starting torque?

a. Centrifugal switch 

b. Thermostat	
c. Start capacitor	
d. Another winding
A

start capacitor

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5
Q

Which of the following devices may be wired into the running circuit of a motor to improve the running efficiency?

a. Start capacitor 

b. Run capacitor	
c. Both a start and run capacitor	
d. Current relay
A

run capacitor

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6
Q

The voltage generated by an electric motor’s rotor turning within a motor is known as __________.

a. continuous coil voltage 

b. back electromotive force (BEMF)	
c. pick-up voltage	
d. drop-out voltage
A

back electromotive force (BEFM)

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7
Q

A(n) _____________ motor is manufactured from special materials that are compatible with refrigerants and oils used in a refrigeration system.

a. hermetic compressor 

b. open split-phase	
c. centrifugal pump	
d. single-phase open
A

hermetic compressors

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8
Q

Two types of motors that are commonly used for hermetic compressor motors are ____________.

a. single-phase open and shaded pole 

b. shaded pole and split-phase	
c. open split-phase and hermetic split-phase	
d. split-phase and permanent split capacitor (PSC)
A

split-phase and permanent split capacitor (PSC)

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9
Q

Power enters a hermetic compressor shell and passes to the motor inside using _____________.

a. start and/or run capacitors 

b. DC converters	
c. insulated motor terminals	
d. separate motor windings
A

insulated motor terminals

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10
Q

Two types of relays that can be used when starting hermetic compressors are _______________ relays.

a. centrifugal and potential 

b. induction and centrifugal	
c. current and potential	
d. induction and current
A

current and potential

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11
Q

A PTCR device is used __________________________.

a. as a pressure protection device 

b. as a motor protection device	
c. as a compressor starting device	
d. to increase motor running efficiency
A

as a compressor starting device

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12
Q

Three-phase motors have __________________.

a. low starting torque 

b. start capacitors wired into the starting circuit	
c. run capacitors wired into the running circuit	
d. high starting torque
A

high starting torque

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13
Q

Large motors with a horsepower greater than 5 are typically ___________ motors.

a. three-phase 

b. single-phase	
c. low-voltage	
d. split-phase
A

three-phase

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14
Q

Two-speed compressor motors are used by some manufacturers to __________.

a. control capacity 

b. run on single-phase and three-phase power supplies	
c. run at varying voltages	
d. increase starting torque
A

control capacity

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15
Q

The rotating portion of a motor that is made of iron or copper bars bound on both ends with aluminum is called the ______________.

a. end bell 

b. winding	
c. rotor	
d. stator
A

rotor

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16
Q

A motor that has two sets of windings, start and run, and has a start capacitor wired in series with its start windings is a ________________ motor.

a. shaded-pole 

b. three-phase	
c. permanent split-capacitor	
d. capacitor-start
A

permanent split-capacitor

17
Q

A motor that has both the start and run windings, along with a run capacitor, energized whenever the motor is energized is a _______________ motor.

a. capacitor-start 

b. permanent split-capacitor	
c. shaded-pole	
d. variable-speed
A

permanent split-capacitor

18
Q

The difference between a motor’s calculated speed and its actual speed is known as ___________.

a. starting torque 

b. induction rate	
c. motor slip	
d. full-load amperes
A

motor slip

19
Q

Capacitors are used after the converter to ________________________.

a. reduce the voltage 

b. suppress the noise	
c. smooth out the DC current	
d. change the voltage frequency
A

smooth out the dc current

20
Q

The converter __________________________.

a. changes the frequency of the power 

b. is used only with DC motors	
c. changes AC to DC	
d. is a switch
A

changes AC to DC

21
Q

The inverter _______________________.

a. adjusts the DC voltage 

b. varies the frequency	
c. smooths out the AC power	
d. contains a capacitor bank
A

varies the frequency

22
Q

A hermetic motor that is cooled by suction gas must have a(n) ______________ to be cooled properly.

a. liquid receiver 

b. refrigerant overcharge	
c. adequate refrigerant charge	
d. accumulator
A

adequate refrigerant charge

23
Q

An electronically commutated motor (ECM) is made up of two components, the _____________________.

a. motor mount and the motor 

b. motor and the shaft	
c. controls and the motor	
d. stator and the rotor
A

controls and the motor

24
Q

On most _____________ motors, the rotation can be reversed by disassembling the motor and turning the stator over.

a. permanent split-capacitor (PSC) 

b. shaded-pole	
c. three-phase	
d. capacitor-start
A

shaded pole

25
Q

A(n) _____________ is used commonly in open split-phase motors to disconnect the start winding from the electrical circuit when the motor reaches approximately 75% of its rated speed.

a. end bell 

b. squirrel cage rotor	
c. centrifugal switch	
d. winding thermostat
A

centrifugal switch

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

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