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Exam 7: Contactors, Motors, and Load Torques

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Question 1

Multiple Choice

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The motor commonly used in computers and digital systems is

A) dc shunt motor
B) Induction motor
C) Stepper motor
D) Synchronous motor.

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Question 2

Multiple Choice

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Most commonly used ac motor is

A) Synchronous motor
B) Slip ring induction motor
C) Squirrel cage induction motor
D) ac commutator induction motor.

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C

Question 3

Multiple Choice

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To save the energy during braking

Regenerative braking mode can be achieved in which quadrant (V-I curve) ?

Belted wound rotor induction motors are preferred for

Which of the following pair is used for frequency converters ?

Reverse motoring mode is available in fourth quadrant.

Pole changing method of speed control is used in

Type-A chopper is used for obtaining which type of mode?

What is the relationship between torque and speed in constant type loads?

A class I contactor should be mechanically sound to withstand

Boost converter is used to _________

In case of contactors, the duty in which the main contacts remain closed for a period bearing a definition relation to the no-load periods, is known as

A motor of less than full load power rating can be used if the load is

Effect of friction torque is more pronounced

The equilibrium speed of a motor load system is obtained

Which one is an example of variable loss?

The cooling time constant is usually

In case of contactors the ratio of the in service period to the entire period, expressed as a percentage is known as

Rolling mills exhibit what type of load torque characteristics?