Deck 22: Variable Frequency Control

Question 1

A decrease in frequency produces a decrease in inductive reactance.

Answer 1

True

Question 2

Many transistor controlled variable frequency drives now employ a special type of transistor called an ____ Bipolar Transistor (IGBT).

A) Inductive Gate
B) Inductive Gas
C) Insulated Gas
D) Insulated Gate

Answer 2

Insulated Gate

Question 3

In a variable frequency drive, the ____ control sets the maximum speed of the motor.

A) minimum hertz
B) maximum hertz
C) current limit
D) volts per hertz

Answer 3

maximum hertz

Question 4

The alternator is turned by a direct current motor or an AC motor coupled to a(n) ____________________ current clutch.

Question 5

Give an overview of alternator control.

Question 6

What is phase paper?

Question 7

Small synchronous motors generally contain ____ slip rings on the rotor shaft.

A) zero
B) two
C) four
D) six

Question 8

When normal excitation has been achieved, the power factor will be ____ percent.

A) 10
B) 33
C) 66
D) 100

Question 9

The field contactor contains a DC coil and is energized by the ____________________ current of the rotor.

Question 10

How do synchronous motors differ from squirrel-cage and wound rotor induction motors?

Question 11

The wound rotor motor was the first alternating-current motor that permitted speed control.

Question 12

The difference between rotor speed and synchronous speed (speed of the rotating magnetic field) is called ____ and is measured as a percentage.

A) wound
B) slip
C) pole
D) hertz

Question 13

The starting current and speed of a wound rotor induction motor is controlled by adding or subtracting the amount of ____________________ connected in the rotor circuit.

Question 14

How does frequency control operate?