BCIT ELTT Level 3 - Motor Control Test Questions and Answers.

BCIT ELTT Level 3 - Motor Control Test
Questions and Answers
Question 1
1 When electromechanical braking is used with an electric motor, the braking system
is operated by a _________ in magnetic DC motor controllers
Correct Answer
C. solenoid



Question 2
7 Which faceplate starter allows speed control?
Correct Answer
B. Four-terminal starter.



Question 3
10 Why can't a standard motor normally use the full frequency range in VFD's?
Correct Answer
B. Motor is not designed for high overspeeds



Question 4
1 Why may an induction motor overheat at low speed on a VFD?
Correct Answer
A Power source does not have a perfect sine wave due to harmonics



Question 5
7 What type of control (armature or field) should be selected for speed control below
the base speed of a motor?
Correct Answer
B. Armature control below base speed




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,Question 6
7 What type of control (armature or field) should be selected for speed control above
speed of a motor?
Correct Answer
C. Field control above base speed.



Question 7
What motor control application would use a VFD with constant torque rating?
Correct Answer
D. Conveyor belts



Question 8
9 What is one disadvantage of friction braking?
Correct Answer
C. The friction parts require periodic maintenance and replacement.



Question 9
12 The outer copper tape shielding in VFD cables helps protect phase conductors
from which two types of interference?
Correct Answer
C. Electromagnetic and electrostatic



Question 10
A VFD allows controlled acceleration, thereby eliminating which of the following?
Correct Answer
D. Mechanical stress




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,Question 11
6 What are the usual types of solid state components used in inverters in VFD's?
Correct Answer
A. SCR's and Transistors



Question 12
5 What is the function of the AC power section in a VFD?
Correct Answer
B. Generate adjustable-frequency AC output



Question 13
An interlocking arrangement on a forward/reverse controller:
Correct Answer
D. Prevents a short circuit condition



Question 14
16. List four actions suggested when troubleshooting the control operation of a
synchronous motor starter.
Correct Answer
A. Check sequence of operation, relay sparking, contactor flash, and switch
operation



Question 15
4 What are the two most common AC-to-AC VFD configurations in use today?
Correct Answer
D. Voltage and Current inverters




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, Question 16
3 List the three sub-systems that a typical VFD controller comprises.
Correct Answer
A. Rectifier, DC link, inverter



Question 17
(Not in module) What is the major advantage of primary-resistance starting over
across-the-line starting?
Correct Answer
C. Reduced line-current disturbance during starting



Question 18
In a plugging circuit with a zero-speed switch, what is the purpose of the control
relay?
Correct Answer
D. Protects from kickback from the zero speed switch



Question 19

6.14 What is the major advantage of regeneration over secondary resistors in speed
regulation in a wound rotor motor?

Correct Answer
D. Regeneration gives higher efficiency



Question 20
7 If an SCR reads zero ohms both ways, what is the problem?
Correct Answer
C. SCR is shorted




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