Electrical Machines- II

What is the operating principle of an alternator?

• Ohm's Law

• Lenz's Law

• Faraday's Law

• Colomb's Law

In a power plant, where is the rotor generally placed:

• Rotor

• Stator

• Exciter

• Shaf

Which of the following is an advantage of a rotating field system?

• Reduces weight of the alternator

• Easy insulation of armature winding

• Provides better cooling

• All of the above

A cylindrical rotor alternator is preferred for:

• Low speed applications

• High speed applications

• Medium speed applications

• None of the above

What is the EMF equation of a power generation?

• E=4.44fTΦKdKpE = 4.44 f T \Phi K_d K_p

• E=2fTΦE = 2 f T \Phi

• E=1.1fTΦE = 1.1 f T \Phi

• E=3.14fTΦKdKpE = 3.14 f T \Phi K_d K_p

Based on the alternator, the relationship between frequency (f), speed (N), and poles (P):

• f=NP60f = \frac{N P}{60}

• f=60PNf = \frac{60 P}{N}

• f=NPf = \frac{N}{P}

• f=PNf = \frac{P}{N}

Pitch factor is used to:

• Increase harmonics

• Reduce harmonics

• Reduce voltage

• Increase spread

Which type of coolant is used for large transformers?

• Air cooling

• Water cooling

• Hydrogen cooling

• Oil cooling

What is the function of an alternator's exciter?

• Provides mechanical power

• Supplies DC to the field winding

• Generates AC voltage

• Reduces losses

Where are the best transformers used:

• High-speed applications

• Low-speed applications

• Medium-speed applications

• None of the above