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Motor ch 14

Adjustable Speed Drives

QuestionAnswer
1. The ___ section of adjustable-speed drives controls the speed and torque of an AC motor by controlling voltage, frequency, and current. inverter
2. A ___ stores energy n the form of a magnetic field. inductor
3 Damage may occur to an AC motor if the supply voltage is varied more than ____ above or below the rated nameplate voltage. 10%
4.Torque decreases when the voltage is lower than rated voltage With 95% of rted voltage, the torque is ___% of rated torque. 90
5. Adjustable-speed drives are called by many names, and often only the word "drive" is used. True or False True
6. Modern drives using pulse-width modulation can use insulated gate bipolar transistors (IGBTs) to create fixed-voltage pulses by switching the transistors ON and OFF at high speed. True or False True
7. The frequency of the voltage used to control motor speed is called the ___ frequency. fundamental. note says know the difference between carrier and fundamental
8. Drives for __ motors are the most complex DC motor drives. compound-wound
9. The ___ frequency of drives is raised above human hearing to eliminate noise concerns. carrier
10. The speed of standard AC squirrel-cage motors is normally varied by changing the number of poles or the ___ applied frequency
11. The carrier frequency of most adjustable-speed motors ranges from 1 kHz to approximately ___ kHz. 16
12. ___ drives that control AC motor speed by setting motor voltage and frequency are relatively inexpensive and work well for most applications. Inverter
13. An advantage standard vector drives have over inverter drives is the vector drives___ have better control of speed and torque
14. Vector drives have many advantages over inverter drives, but inverter drives are more economical and are better for applications that do not require full torque control. True or False True
15. ___ drives can be used to control most types of induction and synchronous motors, and several motors can be operated at the same time. variable-voltage-inverter
16. With DC motors, the frequency is varied to adjust the speed of the motor. True or False True
17. ___ drives must be purchased for each type of motor controlled because they are specific to a particular type of motor Current-source-inverter
18. Chapter 430 of the _____ requires that disconnects be provided for all motors. NEC
19. ___ control is a method of controlling the voltage applied to the armature of a Dc motor. CR armature-voltage
20. The most common DC drives are for ___ motors shunt-wound
21. The volts-per-hertz ratio of an ac motor rated for 460 VAc, 60 Hz opertion is ___ (show work) 7.67
22 see book pge 70
Created by: JoshHampton
 

 



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