Question 1

A direct-current machine can be used as either a motor or generator.

Accepted Answer

A direct-current (DC) machine is designed to operate interchangeably as a motor or a generator depending on the direction of current flow, making it versatile in its application.

Question 2

When plugging, as a general rule, the reversing contactor is of a larger size than the forward contactor because of the increased plugging current.

Accepted Answer

Plugging involves reversing the motor direction, which can result in higher current draw than normal operation, necessitating a larger reversing contactor to handle the increased plugging current safely.

Question 3

When a generator produces electrical power, it produces ____ torque.&#10;A) dynamic&#10;B) counter&#10;C) inductive&#10;D) resistive

Accepted Answer

When a generator produces electrical power, it experiences counter torque, which opposes the motion of the generator's rotor. This is due to Lenz's law, which states that the direction of the induced electromotive force (and therefore the current) in a conductor will be such that it creates a magnetic field that opposes the change in magnetic flux that induced it. This opposition manifests as counter torque in generators.

Question 4

The most accurate method of plug stopping a motor is with a ____.&#10;A) stop switch&#10;B) rotating switch&#10;C) zero speed switch&#10;D) resistor

Accepted Answer

A zero speed switch is the most accurate method for plug stopping a motor because it can detect when the motor has come to a complete stop, ensuring the plug stopping process is accurately timed and executed.

Question 5

Name three methods that can be used to provide braking for a motor.

Accepted Answer

The answer of Name three methods that can be used...

Question 6

Many small single-phase motors change speed by varying the amount of voltage applied to the motor. This method changes the speed of the rotating magnetic field of the motor.

Accepted Answer

The speed of a single-phase motor is primarily determined by the frequency of the supply voltage, not by varying the amount of voltage. Changing the voltage mainly affects the torque and power output, not the speed.

Question 7

Single-phase motors that use a centrifugal switch to disconnect the start windings cannot be used with variable voltage control. This limits the type of induction motors to capacitor-start capacitor-run and ____ motors.

A) capacitor-stop
B) resistor-stop
C) resistor-start resistor-run
D) shaded-pole

Accepted Answer

Shaded-pole motors do not use a centrifugal switch and are suitable for variable voltage control, unlike motors with start windings that need to be disconnected.

Question 8

There are different methods of obtaining a variable AC voltage. One method is with the use of an autotransformer with a ____ tap.&#10;A) sliding&#10;B) fixed&#10;C) universal&#10;D) resistor

Accepted Answer

An autotransformer with a sliding tap allows for the adjustment of the output voltage by changing the tap position, thus providing a variable AC voltage. Fixed taps would not allow for variable voltage adjustment, and the terms "universal" and "resistor" do not apply to the type of tap used in autotransformers for this purpose.

Question 9

One type of alternating current motor that can use variable voltage for speed control is the ____________________ or AC series motor.

Accepted Answer

The answer of One type of alternating current motor that...

Question 10

Give an overview of universal motors.

Accepted Answer

The answer of Give an overview of universal motors....

Question 11

A two-speed motor will contain six T leads in the terminal connection box.

Accepted Answer

The answer of A two-speed motor will contain six T...

Question 12

A three-phase two-pole motor contains ____ actual poles.&#10;A) two&#10;B) three&#10;C) four&#10;D) six

Accepted Answer

The answer of A three-phase two-pole motor contains ____ actual...

Question 13

Consequent pole motors intended to operate with four speeds use ____ windings.&#10;A) two reconnectable&#10;B) three reconnectable&#10;C) two separate&#10;D) three separate

Accepted Answer

The answer of Consequent pole motors intended to operate with...

Question 14

What is one advantage of consequent pole motors over some others types of variable speed alternating current motors?

Accepted Answer

The answer of What is one advantage of consequent pole...

Deck 21: Braking , Consequent Pole Motors, Variable Voltage and Magnetic Clutches