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Transformers ch 8

Reactors and Isolation Transformers

QuestionAnswer
1. A __ is a distortion in a voltage waveform where the voltage quickly drops toward zero and then returns to the correct value( Choke; Notch; Relay; Switch) Notch
2. __ is the opposition to current flow in an AC circuit. (Choking; Impedance; Reactance; Shielding) Reactance
3. A __ is an inductor whose inductance is controlled through the use of a magnetic field created by a second winding wound around the same iron core as the primary winding. (Next Card)
(Common-mode choke; Drive isolation transformer; Saturable-core reactor; Silicon-controlled rectifier) saturable-core reactor
4. Electric motors typically draw many times their full-load current during startup. T/F True
5. A reactor should have about __ impedance to reduce notch depth by about 50% (3%; 5%; 10%; 12%) 3%
6. All two-winding transformers are isolation transformers. T/F True
7. __ is a type of electromagnetic interference induced on power or communication lines ( Common-mode noise; Notching; Resonance; Zero-switching) Common-mode noise
8. A __ is a reactor used to reduce common-mode noise current generated by the rapid switching of a motor drive or a signaling device . ( next card) Common-mode choke
(Capacitor bank; Common-mode choke; Isolation transformer; Silicon-controlled rectifier) Common-mode choke
9. In a saturable-core reactor, large amounts of DC current can be controlled by a small amount of AC current. T/F False
10. Zero-crossover are often used for timing signals and to activate equipment T/F True
11. With a variable-frequency drive, unwanted pulses of current are caused by fast-changing voltages from the drive T/F True
12. Explain the formation of voltage notches when using SCRs Two SCR are fired at the same time
13.Explain the rationale for reducing notch depth by 50% . Why not more? Or less?
14. A saturable-core reactor consists of one winding T/F False
15. Electrostatic shields can prevent common-mode noise from transferring from the transformer's primary to the secondary only if the secondary is grounded T/F False; secondary ungrounded
16. __ help eliminate voltage spikes by slowing down the rate of change in the drive output voltage. ( Drive isolation transformers; Output reactors; Output rectifiers; Variable-frequency drives) Output reactors
17. To reduce notching, a reactor can be used to add impedance. the added impedance__ (next card_
(Decreases notch depth & narrows notch width; Decreases notch depth and widens notch width
18. List the three basic functions of a drive isolation transformer page 148
19. A __ is a reactor used to restrict the current to AC or DC drives in the case of short circuits in the drive itself Choke
20. A drive isolation transformer is designed with additional __ to reduce power quality problems associated with nonlinear loads ( flux; reactance; resonance; shielding) reactance
21. List 3 benefits associated with grounding the secondary of a drive isolation transformer p 149
22. The secondary of a drive isolation transformer represents a separately derived system T/F True
23. List 3 uses for line input reactors p 141
24. Nonlinear rectified power supplies are a common cause of power quality problems T/F True
25. A ___ is a coil added in series with a load to reduce inrush current, voltage notching effects, and voltage spikes ( capacitor; plolarized-frequency relay; reactor; silicon-controlled rectifier_ Reactor
26. Rectifiers are ;used in the starters of large synchronous motors to provide a voltage to the AC coil of the polarized-frequency relay T/F False
27. HOw are drive isolation transformers and line reactors similar? Which can provide additional benefits, and what are they? p 150
28.Match the picture p 105
Created by: JoshHampton
 

 



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