Unit 17 Quiz Part 2 Flashcards by Stirling Ragasa | Brainscape

Q

As temperature increases, a PTC’s resistance will _______.

A

Increase

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Q

Hermetic compressors may be cooled internally by _____ and/or externally by ____.

A

1.Vapor
2. Air

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Q

Pulsating DC voltage is produced in the ______section of the VFD.

A

Rectifier

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Q

Four types of devices are commonly used to disconnect the start capacitor from the circuit. What are the four devices?

A

Centrifugal, potential relay, current relay, and PTCR

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Q

True or false: DC motors with brushes cannot be used in hermetic compressors.

A

True

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Q

True or false: To measure the resistance of a PTCR, wait until it cools to room temperature and then check its resistance.

A

True

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Q

True or false: The run and start winding resistance in a three-phase motor should add up to the resistance measured from the start and run winding.

A

False

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Q

True or false: Transistors can be found in the rectifying section of the VFD.

A

False

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Q

True or false: The term “soft starting” for a VFD means a motor is slowly ramped up to speed instead of starting at full speed and drawing locked rotor amperage.

A

True

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Q

True or false: The capacitors in parallel filter the voltage wave and the inductor filters the current wave in a VFD.

A

True

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Q

True or false: A three-phase dual voltage motor is wired in series when using low voltage configuration.

A

False

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Q

True or false: A 230V capacitor can be used for a 440V application.

A

False

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Q

Match the component/function with the proper section of a VFD. Switching (S), Filter (F), Rectification (R).

Transistors

A

S

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Q

Match the component/function with the proper section of a VFD. Switching (S), Filter (F), Rectification (R).

Diodes

A

R

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Q

Match the component/function with the proper section of a VFD. Switching (S), Filter (F), Rectification (R).

Inductor

A

F

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Q

Match the component/function with the proper section of a VFD. Switching (S), Filter (F), Rectification (R).

SCR

A

R

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Q

Match the component/function with the proper section of a VFD. Switching (S), Filter (F), Rectification (R).

Convert DC to AC

A

S

Q

Match the component/function with the proper section of a VFD. Switching (S), Filter (F), Rectification (R).

Capacitor

A

F

Q

Match the component/function with the proper section of a VFD. Switching (S), Filter (F), Rectification (R).

PWM

A

S

Q

Match the component/function with the proper section of a VFD. Switching (S), Filter (F), Rectification (R).

Converts AC to DC

A

R

Q

Match the component/function with the proper section of a VFD. Switching (S), Filter (F), Rectification (R).

Inverter

A

S

Q

Holds the motor components in place and provide a means for securely mounting the motor itself.

A

Housing

Q

Has less windings and resistance than the start winding.

A

Run windings

Q

Winding resistance is the same in each winding.

A

3-phase motor

Q

Switching section of a VFD.

A

Inverter

Q

The maximum EMF that the relay’s coil can tolerate continuously without overheating and opening the circuit.

A

Continuous coil voltage

Q

Electronic device in a motor circuit that is used to control motor speed for variable speed motors.

A

PWM

Q

The speed at which power devices switch on and off.

A

Switch/carrier frequency

Q

Uses electronics to commutate the rotor instead of brushes.

A

ECM motor

Q

More efficient to reduce the speed of a motor than to stop and start.

A

Variable speed motor

Q

Very little starting torque and can be reversed by flipping the stator.

A

Shaded pole motor

Q

Why can’t you have a centrifugal switch in a hermetic compressor?

A

An ARC may occur that would result in a explosion potentially occurring spark degrades refrigerant (sludge, acid)

Q

How is a typical open electric motor cooled?

A

Air cooled

Q

Motor wire configurations may use 3,6,9 or 12 lead wires. What wire leads can be configured in either the wye or delta configuration for dual voltage operation?

A

9 & 12

Q

What wire leads can only be configured for single voltage operation?

A

3 & 6

Q

Extra Credit
1. When joining Steel pipe, approximately how many perfect threads and imperfect threads for each joint?

A

7 perfect & 2/3 imperfect

Q

Extra credit:
2. Nominal tubing used for plumbing is sized by its ____ diameter while ACR tubing is sized by its ____ diameter.

A

Inner
Outer

Q

Extra Credit:
3. What type of fastener is used to hold a component either onto a shaft or inside some type of housing?

A

Cotter pin
Retaining/snap-ring
Hairpin

Q

Extra Credit:
4. When charging a chiller, refrigerant vapor is introduced into the system before charging with liquid refrigerant because _____.

A

Liquid charged into a deep vacuum will cause the refrigerant to boil and may lower temperatures enough to freeze the water in the tubes

Q

Extra Credit:
5. ______ + _________+________= acids

A

Heat + moisture + refrigerant = acids