AC Generators

Question 1

What things are required to produce an EMF by Induction?

Answer 1

1. An electrical conductor
2. A magnetic field
3. Relative movement

Question 2

What is the most common type of generator in use today?

Answer 2

Brushless Generator

Question 3

List the things that the generated EMF output will depend upon?

Answer 3

1. The amount of lines of flux cutting across the conductor (voltage)
2. The speed at which the lines of flux pass the conductor (frequency)

Question 4

What is fitted to the AC generator to make it turn? Give 2 examples used in HM Ships.

Answer 4

1. Prime mover
2. Diesel engine
3. Gas turbine unit

Question 5

How is the HF Generator turned, what is its output and where is it fed to?

Answer 5

• Belt driven
• 115V - 1 phase - 1600Hz
• Fed to the Automatic Voltage regulator (AVR)

Question 6

What sort of current is fed into the Exciter Stator?

Answer 6

DC

Question 7

What is the purpose of the Rectifier assembly?

Answer 7

To convert the AC input from the Exciter Rotor into a DC output to the main AC Generator Rotor

Question 8

How can the voltage generated by an AC generator be altered?

Answer 8

by increasing or decreasing the strength of the magnetic field

Question 9

If the magnetic field around the AC Generator Rotor is stable (made from a DC supply), how does the Generator produce an AC output?

Answer 9

When the rotating magnetic field cuts through the Stator windings it produces the AC output voltage

Question 10

What is the output from Generators fitted to HM Ships and how does the AVR know what’s being produced?

Answer 10

• 450V - 60Hz - 3 phase
• The AVR takes a sample using a sensing line