Alternators

As the speed of an alternator increases, the frequency

• Increases

• Decreases

• Remains constant

• May increase or decrease depending on the power factor

The generator which gives dc supply to the rotor of an alternator is called

• Converter

• Exciter

• Inverter

• Rectifier

The rotor of alternator has

• No slip rings

• 2 slip rings

• 3 slip rings

• 4 slip rings

Alternator works on the principle of

• Self and mutual induction

• Self induction

• Mutual induction

• Faraday’s law of electromagnetic induction

Alternators are also called Synchronous generators because

• They must run at a constant speed irrespective of desired frequency.

• They must run at synchronous speed to give the desired frequency

• They must run at a speed which varies with frequency.

• They must run at a speed equal to the desired frequency.

A machine without commutator, providing an ac emf to the external circuit is called as

• D.C. generator

• Alternator

• Transformer

• Synchronous motor

Practically, most of the alternators prefer which type of construction?

• Rotating field type

• Rotating armature type

• Both are equally important

• None of these

In synchronous machine, poles are made up of thick steel laminations. In salient pole type rotor

• Poles are projected out from the surface of the rotor

• The unslotted portions of the cylinder itself acts as the poles

• Both (a) and (b)

• None of the above

Salient pole type rotors are generally used for the range of 125 rpm to 500 rpm. The limiting factor for the size of the rotor is the

• Rotating field type construction

• Centrifugal force acting on the rotating member

• Rotating armature type construction

• All of above

The diameter and axial length of rotors of smooth cylindrical type rotors are

• Small diameter, small axial length

• Large diameter, large axial length

• Large diameter, small axial length

• Small diameter, large axial length