The speed of a three-phase squirrel cage induction motor is controlled by the frequency of the applied voltage and _____.
a. voltage dropping resistors
b. the number of poles
c. full-load torque
d. armature current
b. the number of poles
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Answer the following statement(s) true (T) or false (F)
1. Large motors should be connected directly across the line on startup. 2. In the event of a power failure, a manual starter motor automatically restarts when the power returns. 3. Common applications of automatic starters provide control of small machine tools, fans, pumps, oil burners, blowers, and unit heaters. 4. When an overload relay trips, the starter mechanism unlatches, opening the contacts to stop the motor. 5. Only one overload relay is required in either the single-pole or double-pole motor starter.
How can the centrifugal compressor speed be higher than the motor speed?
A) By using speed-increasing gears B) By using a drive belt with a smaller pulley on the motor than on the compressor C) Because of the inertia of the impeller D) By using a drive belt with a larger pulley on the motor than on the compressor
The direction of the rotor can be reversed by changing the position of ____________________.
Fill in the blank(s) with the appropriate word(s).
To produce more output change per input change, the proportional band is ____.
A. increased B. decreased