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Exam 7: Contactors, Motors, and Load Torques

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Question 1

Multiple Choice

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

A) Motoring mode
B) Regenerative braking mode
C) Reverse motoring mode
D) Reverse regenerative braking mode

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Question 2

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Reverse motoring mode is available in fourth quadrant.

A) True
B) False
C) none
D) all of the above

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Question 3

Multiple Choice

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The cooling time constant is usually

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

The motor commonly used in computers and digital systems is

Which of the following pair is used for frequency converters ?

Effect of friction torque is more pronounced

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

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

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

Rolling mills exhibit what type of load torque characteristics?

To save the energy during braking

The equilibrium speed of a motor load system is obtained

Which one is an example of variable loss?

Boost converter is used to _________

A class I contactor should be mechanically sound to withstand

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

Most commonly used ac motor is

Belted wound rotor induction motors are preferred for

Pole changing method of speed control is used in