1. DC motors are still used in many industries.
a. True
b. False
2. Variable-frequency drives control motor speed by controlling the frequency of the power supplied to the motor.
a. True
b. False
3. IGBTs have an insulated gate different from all types of field effect transistors (FETs).
a. True
b. False
4. The magnet wire used in the construction of inverter rated motor windings has a lower rated insulation than other
motors.
a. True
b. False
5. The primary purpose of a variable-frequency drive is to provide speed control for an AC motor.
a. True
b. False
Name: Class: Date:
Unit 55 AC Adjustable Frequency Drives
6. Drives using IGBTs generally use ____ to rectify the AC voltage into DC.
a. SCRs b. GTOs
c. diodes d. thyristors
7. Inverter-rated motors generally have phase paper ____.
a. to provide a larger surface area
b. to provide continuous cooling for the motor
c. to help draw air through the motor
d. added to the terminal leads
8. Many variable-frequency drives can provide the ____ characteristic that is so desirable in DC motors.
a. low-speed torque b. low power factor
c. high-speed torque d. high power factor
9. Speed regulation is accomplished by sensing the speed of the motor and ____.
a. connecting current transformers to the input of the drive
b. feeding this information back to the drive
c. sensing the increase in current as load is added
d. adjusting this speed
Name: Class: Date:
Unit 55 AC Adjustable Frequency Drives
10. The values of current limit, speed, ramping time, and so on for variable-frequency drives are ____.
a. more difficult to adjust
b. less accurate than adjusting trim resistors
c. hard to read
d. programmed into the unit
Name: Class: Date:
Unit 55 AC Adjustable Frequency Drives