Voltage Regulation of Alternator or Synchronous Generator
Table of Contents
Voltage Regulation of Alternator
When a load is reduced from its Full-load rated value to zero, the voltage Regulation of an Alternator or Synchronous generator is defined as the rise in the Terminal voltage. The Alternator’s speed and field current remain constant.
In other words, the change in Terminal voltage from no-load to full load rated value divided by the Full-load rated voltage can be used to define the Alternator’s voltage Regulation. i.e.,
Per unit voltage regulation= {|Ea|−|V|} / |V|
Also, the Percentage voltage Regulation of the Alternator is given by,
Percentage voltage regulation={|Ea|−|V|}×100% / |V|
Where,
- |𝐸𝑎| is the magnitude of generated voltage (or no-load voltage) perphase
- |𝑉| is the magnitude of full-load rated terminal voltage per phase
The alternator’s figure-of-merit is analogous to the voltage regulation. A synchronous generator or alternator’s voltage regulation value should be as low as possible for optimal performance. The voltage regulation value is zero for a perfect alternator.
The voltage regulation of an alternator depends upon the power factor of the load, i.e.,
- An Alternator operating at a unity power factor has a small positive voltage Regulation.
- An Alternator operating at a lagging power factor has a large positive voltage Regulation.
- An Alternator operating at lower leading power factors, the voltage rises with increase of the load and hence, the voltage Regulation is negative.
- For a certain leading power factor, the full-load voltage Regulation is zero. In this case, both the full-load and no-load Terminal voltages are the same.
Voltage Regulation of Alternator using Direct Loading Method
The alternator is run at Synchronous speed and its terminal voltage is set to its rated value for the direct load test (V). Once the ammeter and Wattmeter connected to the test circuit show the rated values at the specified power factor, the load is changed. The alternator’s speed and field excitation are then maintained at a constant level while the load is removed, and the no-load voltage (Ea) of the Alternator is recorded. These values can be used to determine the Alternator’s voltage Regulation as follows:
Percentage voltage Regulation= {|Ea|−|V|}×100% / |V|
Only small Alternators with power ratings under 5 kVA are suitable for the direct load test of the alternator to determine voltage regulation. The Voltage Regulation of Alternator is determined for large alternators using the three indirect methods listed below,
which are as follows:
- Synchronous impedance method or EMF method.
- Ampere-turn method or MMF method.
- Zero power factor method or Potier triangle method.
What is voltage regulation for generator?
The difference in the voltage drop from no load to full load to full load voltage is referred to as a generator’s voltage regulation. The field and armature are connected in series in a series generator. Any increase in load current raises the field, which in turn raises the terminal voltage.
voltage Regulation types?
There are two main types of voltage Regulators: linear and Switching