AC Machines Technical Quiz

The basic function of a transformer is to change

• the level of the voltage

• the power level

• the power factor

• the frequency

In a shaded pole motor, shading coils are using to

• reduce winding losses

• reduce friction losses

• produce rotating magnetic field

• protect against sparking

The capacitor in a capacitor-start induction run ac motor is connected in series     with

• starting winding

• running winding

• squirrel cage winding

• compensating winding

why is a centrifugal switch  used in a 1-ph induction motor

• To protect the motor from overloading

• To improve the starting performance of the motor

• To cut off the starting winding at an appropriate instant

• d)    To cut in the capacitor during running conditions

Induction generators deliver power at

• Leading power factor only

• Lagging power factor only

• Leading as well as lagging power factor

• Unity power factor only

The method that gives continuous speed control of a slip-ring induction motor is

• Rotor resistance control

• Secondary foreign voltage control

• Concatenation or cascade operation

• Line voltage control

During plugging of an induction motor

• Phase sequence is reversed

• A dc source is connected to stator

• One phase is open-circuited

• v

The good power factor of an induction motor can be achieved if the average flux density in air gap is

• Large

• Small

• Infinite

• Absent

An induction motor with 1000 rpm speed will have __________ poles

• 2

• 6

• 4

• 8

Which of the following equipment will draw the reactive power?

• Electrical iron

• Tubelight

• Three phase motor

• rectifier