Chapter 11 - Control Of Generator Output Voltage.

Question 1

Explain Why A Voltage Regulator Is Necessary?

Answer 1

Voltage regulation is needed to maintain voltage relativity constant from no load to full load, the amount of field excitation current to the rotor is alterd

Question 2

explain how hand control of a generator is achieved?

Answer 2

Decreasing the resistance of the Hand regulator increases the field current of the DC exciter causing more excitation current to pass to the rotor of the main generator, Thus increasing output Voltage.

Question 3

List each component of the A.V.R?Explain the purpose of

Answer 3

1. Transformer/Rectifier Unit.
2. Reference Voltage Unit.
3. Comparator Unit.
4. Thyristor Bridge Rectifier.

Question 4

Explain the purpose of Transformer/Rectifier Unit in a A.V.R?

Answer 4

The T.R.U Senses the output voltage of the generator and transforms & Rectifies it to produce a lower DC Voltage proportional to the generator output voltage.

Question 5

Explain the purpose of Reference Voltage Unit in a A.V.R?

Answer 5

The R.V.U produces a DC Voltage proportional to the desired output voltage set by the Operator.

Question 6

Explain the purpose of Comparator Unit in a A.V.R?

Answer 6

The Comparator Unit compares the voltage signal from the T.R.U with the reference Voltage signal. it output is equal to the difference of the 2 voltages

(V reference - V actual)

This sends a pulse signal to the thyristor Bridge.

Question 7

Explain the purpose of Thyristor Bridge Rectifier in a A.V.R?

Answer 7

controls the amount of current to the exciter field

Question 8

What are the Requirements for voltage control with an A.V.R?

Answer 8

There are two typical requirement for voltage control with a A.V.R

1. from no load to full load the maximum change in terminal voltage must be less than 1%
2. For a suddenly applied Load, voltage must not change by more than 15% and must be back within 1% of the desired voltage within one second.

Question 9

Explain the operation of an A.V.R if a Large inductive load is added?

Answer 9

If a large inductive load such as a big motor is started, then the large inductive load will cause voltage to drop.

The T.R.U would sense the change in voltage.
The Comparator would compare actual and reference voltages and would produce a voltage signal of the difference the of the voltage drop.
The tyristor bridge would then produce an increased current to the field of the exciter.
The Main Exciter will generate a larger field current for the main generator. thus increasing Field Flux which will result in a higher generated E.M.F.
If E.M.F increases then terminal voltage will also go up till it reaches the operator’s set value.

Question 10

Define Voltage Regulation?

Answer 10

Voltage Regulation is a percentage measure of how much a generator’s voltage changes between No Load & Full Load conditions.