Chapter 8 - Intro to AC Generators

Question 1

Explain why the armature of most A.C generators is on the stator instead of the rotor.

Answer 1

There are three main advantages to having the armature on the stator in stead of the rotor.

1. The armature can no be made of many heavy loops because centrifugal force is no longer a problem
2. due to the rotating field being lighter greater rotational speed can achieved.
3. slip ring no longer required due to stationary terminal on the armature.

Question 2

Explain why DC Machines have communtator and Brushes

Answer 2

the communtator is needed in a dc machine to ensure that the current flows in the same direction through the windings

Question 3

Explain why AC Machines have Sliprings?

Answer 3

because the current Alternates there is no need to ensure current flows in the same direction

Question 4

Explain 3 ways to increase E.M.F in a AC Generator?

Give the Limitations of each

Answer 4

1. Increase the field strength. (limited by Magnetic Saturation of the poles)
2. Increase rotational Speed. (Limited by Centrifugal Forces)
3. Add More Loops to the Armature and put them in Series with each other. (limited by centrifugal forces and the size of the rotor.

Question 5

Explain 2 ways of Increasing the frequency output of an AC Generator?

Answer 5

Increase the number of poles pairs in the generator increases frequency.