1. A frequency changer may be used to vary the speed of AC squirrel cage induction motors.
a. True
b. False
2. There is only one method used for one or more motors to obtain variable frequency from a fixed-frequency power
source.
a. True
b. False
3. Variable-frequency power drives are used on many different types of conveyor systems.
a. True
b. False
4. Assembly lines make use of variable-frequency power drives.
a. True
b. False
5. Variable pitch systems are among the lowest-cost methods of achieving variable speed.
a. True
b. False
Name: Class: Date:
Unit 54 Variable-Frequency Mechanical Drives
6. The speed of an AC squirrel cage induction motor depends on the frequency of the supply current and ____.
a. power-factor correction b. the motor unit size
c. the response accuracy d. the number of poles of the motor
7. In cases where more than one motor is involved, all of the motors are connected electrically to the power system of
the ____.
a. input source b. alternator
c. pulleys d. output source
8. Variable pitch pulleys is a mechanical method of obtaining continuously adjustable speed from ____.
a. the direct motor drive b. motor input
c. constant speed shaft d. the output to the alternator
9. Screw conveyors may be controlled individually by variable drive ____ motors.
a. slave b. coupled
c. remote d. series
10. A variable power unit may be used to control one or more motors at ____ speeds.
a. homogeneous b. incremental
c. coordinated d. high
Name: Class: Date:
Unit 54 Variable-Frequency Mechanical Drives