Deck 34: Variable Voltage and Magnetic Clutches

Question 1

A(n) ____________________ is a solid-state device similar to a silicon controlled rectifier (SCR), except that it will conduct both the positive and negative portions of a waveform.

Answer 1

triac

Question 2

One method of obtaining a variable AC voltage is with the use of an autotransformer with a sliding tap. The sliding tap causes a change in the turns ratio of the ____________________.

Answer 2

transformer

Question 3

Motors that used a centrifugal switch to disconnect the start windings cannot be used with variable voltage control.

Answer 3

True

Question 4

What is the main advantage of an eddy current clutch?

Question 5

Clutches cannot provide a smooth start for loads that can be damaged by sudden starting, or for high inertia loads such as centrifuges or flywheels.

Question 6

____________________ are used in applications where it is desirable to permit a motor to reach full speed before load is applied.

Question 7

Motors that are intended to operate with variable voltage are designed with ____________________ stators.

Question 8

Figure 34-6
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The accompanying diagram has a double-face magnetic clutch.

Question 9

What are the disadvantages of motors that contain high impedance stator windings?

Question 10

Double-face clutches have both the armature and field discs mounted on the same hub.

Question 11

What does the high impedance of the stator prevent?

Question 12

Figure 34-8


In the accompanying diagram, what do part A and part B show?

Question 13

Magnetic clutches are divided into three components. What are they?

Question 14

The problem with eddy current clutch circuits is that they lack a speed sensing device that automatically increases or decreases the DC excitation current when load is added or removed.

Question 15

Only triac controls that are designed for use with ____________________ loads should be used to control a motor.