Module 4 Flashcards
a device that controls a physical quantity in relation to a reference value
Servomechanism
a generator in which the output is controlled by small variations in the current in the field coils; a dc amplifier
Amplidyne
the oscillation of a mechanical system about the desired position
Hunting
What is the name for a device that controls a physical quantity in relation to a reference value?
Servomechanism
To keep a regulated quantity matched to a reference value, a servomechanism needs four characteristics. What are they?
Fast response
High accuracy
Unattended control
Remote control
The _____ of a servomechanism actually makes the changes in the physical system.
Output controller
The direction in which a servomotor rotates is determined by the phase relationship between the power applied to the _____ field and the _____ field.
Fixed, Control
Once the control transformer produces an error signal, the servomotor continues to turn until the rotor of the control transformer returns to _____.
Electrical Zero
In the closed-loop servosystem, at the static position of electrical zero, the output of the input controller is _____.
Zero
When using electrodynamic control for a dc motor, the input to the motor is controlled by the _____.
Generator
An amplidyne generator has two sets of brushes. One set is _____, and the other supplies power to the _____.
Short-circuited; Servomotor
The oscillation of a mechanical system about the desired position is called _____.
Hunting
The magnetic field in a servomotor is usually produced by a(n) _____, but sometimes by _____.
Field winding; Permanent magnets
In a dc servomotor, loss of magnetism in permanent magnets can be avoided by adding a(n) _____ in series with the armature.
Compensating winding
Most ac servomotors are not as good as dc servomotors, because they lack the range of _____.
Speed control
The rotor in an ac servomotor is either a(n) _____ or a(n) _____ rotor.
Wound, Squirrel cage
A capacitor motor is reversed either by reversing the connections to one ______, or by shifting the _____ to the other coil.
Stator coil; Capacitor
The speed of a capacitor motor is varied by changing the applied _____.
Potential difference
What is another name for a drive motor?
Servo actuator
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
a. attended control
In an amplidyne, the ratio of the power output to the power input can be as high as
10,000
Once the control transformer produces an error signal, the servomotor turns until the rotor of the control transformer
Returns to electrical zero
If the strength of the control field decreases in an amplidyne, the output of the armature
decreases in proportion.
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
zero
Inertia causes a servomechanism to
over travel the desired position
The amplidyne generator is actually a dc
amplifier
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
b. Compensating winding
How many sets of brushes are located on the commutator of an amplidyne generator?
Two
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
d. all of the above
