Deck 15: Variable Frequency Drive Principles

Question 1

One benefit of VFD technology is that the motor can be operated at different speeds above and below its rated _______________ speed.

Answer 1

synchronous

Question 2

Only ____-phase motors are suitable for use with VFDs.

A)one
B)two
C)three
D)four

Answer 2

C

Question 3

Most home motors are specialized, ____ motors.

A)standard induction
B)standard magnetic
C)fractional magnetic
D)fractional horsepower

Answer 3

D

Question 4

The principles that demonstrate the affect of motor speed on pump and fan flow, pressure, and horsepower are defined by the _______________ laws.

Question 5

The _______________ principle is basically a ratio of the voltage applied to the motor, divided by the frequency applied to the motor.

Question 6

____ is what happens when the induction motors stops functioning like a motor, and starts functioning like a generator instead.

A)Regeneration
B)Regrowth
C)Torque
D)Rotation

Question 7

A ____ drive is a motor controller that controls the primary supply frequency of the electrical.

A)variable-frequency
B)standard-frequency
C)voltage
D)electricity

Question 8

PWM stands for _______________.

Question 9

A magnetic motor is a ____-quadrant control device.

A)single
B)double
C)triple
D)quadruple

Question 10

VFDs are usually designed for operating characteristics of ____ motors.

A)NEMA design A
B)NEMA design B
C)NEMA design C
D)NEMA design D

Question 11

The ____ changes the DC bus power to a controlled frequency AC on the output.

A)inverter
B)dc bus
C)rectifier
D)control and regulation

Question 12

When using the _______________ contactor across the line full voltage motor starting method, the electrical supply power to the motor is either full on, or completely off.

Question 13

It's estimated that the average home has about ____ electric motors.

A)25
B)50
C)75
D)100

Question 14

The mode of operation for motors operated above their rated frequency is called ____ horsepower.

A)continual
B)variable
C)stable
D)constant

Question 15

The rectifier is also called a(n) ____.

A)converter
B)dc bus
C)inverter
D)regulation

Question 16

The ____ stage of the VFD prepares the DC power from the rectifier stage, for use by the inverter stage.

A)inverter
B)dc bus
C)rectifier
D)control and regulation

Question 17

____ torque mechanical loads are machine applications where the torque loading is a function of the speed; low torque at low speeds, and higher torque at higher speeds.

A)Variable
B)Constant
C)Frequent
D)Average

Question 18

The ____ section of the VFD senses the CEMF of the motor to make adjustments and regulate the inverter section output.

A)inverter
B)dc bus
C)inverter
D)control and regulation

Question 19

The stage of the VFD that converts the AC input power to DC power is called the ____.

A)inverter
B)dc bus
C)rectifier
D)regulator

Question 20

_______________ torque applications require the same amount of driving torque throughout the entire operating speed range.

Question 21

Quadrants 2&4 are referred to as _______________ quadrants, because torque and rotation are in opposite directions.

Question 22

Name and describe the four stages of the VFD.

Question 23

What is the affinity laws?

Question 24

Quadrants 1&3 are referred to as _______________ quadrants, because both torque and rotation are in the same direction.