Module 4

Question 1

a device that controls a physical quantity in relation to a reference value

Answer 1

Servomechanism

Question 2

a generator in which the output is controlled by small variations in the current in the field coils; a dc amplifier

Answer 2

Amplidyne

Question 3

the oscillation of a mechanical system about the desired position

Answer 3

Hunting

Question 4

What is the name for a device that controls a physical quantity in relation to a reference value?

Answer 4

Servomechanism

Question 5

To keep a regulated quantity matched to a reference value, a servomechanism needs four characteristics. What are they?

Answer 5

Fast response
High accuracy
Unattended control
Remote control

Question 6

The _____ of a servomechanism actually makes the changes in the physical system.

Answer 6

Output controller

Question 7

The direction in which a servomotor rotates is determined by the phase relationship between the power applied to the _____ field and the _____ field.

Answer 7

Fixed, Control

Question 8

Once the control transformer produces an error signal, the servomotor continues to turn until the rotor of the control transformer returns to _____.

Answer 8

Electrical Zero

Question 9

In the closed-loop servosystem, at the static position of electrical zero, the output of the input controller is _____.

Answer 9

Zero

Question 10

When using electrodynamic control for a dc motor, the input to the motor is controlled by the _____.

Answer 10

Generator

Question 11

An amplidyne generator has two sets of brushes. One set is _____, and the other supplies power to the _____.

Answer 11

Short-circuited; Servomotor

Question 12

The oscillation of a mechanical system about the desired position is called _____.

Answer 12

Hunting

Question 13

The magnetic field in a servomotor is usually produced by a(n) _____, but sometimes by _____.

Answer 13

Field winding; Permanent magnets

Question 14

In a dc servomotor, loss of magnetism in permanent magnets can be avoided by adding a(n) _____ in series with the armature.

Answer 14

Compensating winding

Question 15

Most ac servomotors are not as good as dc servomotors, because they lack the range of _____.

Answer 15

Speed control

Question 16

The rotor in an ac servomotor is either a(n) _____ or a(n) _____ rotor.

Answer 16

Wound, Squirrel cage

Question 17

A capacitor motor is reversed either by reversing the connections to one ______, or by shifting the _____ to the other coil.

Answer 17

Stator coil; Capacitor

Question 18

The speed of a capacitor motor is varied by changing the applied _____.

Answer 18

Potential difference

Question 19

What is another name for a drive motor?

Answer 19

Servo actuator

Question 20

In a servomechanism, all of the following are needed to keep a regulated quantity matched to a reference value, except

a. attended control
b. fast response
c. high accuracy
d. remote control

Answer 20

a. attended control

Question 21

In an amplidyne, the ratio of the power output to the power input can be as high as

Answer 21

10,000

Question 22

Once the control transformer produces an error signal, the servomotor turns until the rotor of the control transformer

Answer 22

Returns to electrical zero

Question 23

If the strength of the control field decreases in an amplidyne, the output of the armature

Answer 23

decreases in proportion.

Question 24

If the rotor of the follow-up control transformer makes an angle of 90* with the field axis, the potential difference induced across the rotor is

Answer 24

zero

Question 25

Inertia causes a servomechanism to

Answer 25

over travel the desired position

Question 26

The amplidyne generator is actually a dc

Answer 26

amplifier

Question 27

Which of the following can prevent loss of magnetism in a permanent-magnet servomotor?

a. Antihunt device
b. Compensating winding
c. Consequent winding
d. Killer winding

Answer 27

b. Compensating winding

Question 28

How many sets of brushes are located on the commutator of an amplidyne generator?

Answer 28

Two

Question 29

An ac induction motor can be modified to obtain speed control and higher starting torque by

a. adding a tapped autotransformer
b. increasing the end-ring resistance
c. increasing the rotor-bar resistance
d. all of the above

Answer 29

d. all of the above