A generator should always be efficient enough to keep the voltage stable. That’s because if the voltage fluctuates while working, it might damage the appliances. A sudden shift in voltage amount can cause unwanted sparks in the devices. For this purpose, we use an automatic voltage regulator for the generator.

An automatic voltage regulator is a crucial part of the alternator (Generator). So, let’s discuss what an Automatic Voltage Regulator is. And what it does do.

What is an Automatic Voltage Regulator (AVR) for generators?

An automatic voltage regulator regulates the voltage of the generator. It takes the fluctuating voltage and adjusts it to a constant voltage. When the supply system goes through some variation, fluctuation occurs. This voltage can be harmful to the appliances as it can damage the equipment of the power system.

The generator can control this variation by installing an automatic voltage regulator as voltage fluctuation can occur at various places. The manufacturer provides AVR at more than one point. This helps in controlling the voltage variations at each end.

The AVR comes with a generating set when you buy a new generator. This also depends on the model or the accessories that can fit the generator. So each generator has its kind of AVR.

What is the working principle of a voltage regulator?

The basic principle behind a voltage regulator is the detection of errors (Sivaranjath, 2018). At first, the potential transformer provides the voltage. It is then rectified, filtered, and compared with a reference voltage.

This comparison makes to check. If there’s some fluctuation from the standard amount or not. If some difference comes out, the regulator highlights it.

The stabilizer works by stabilizing the output voltage of generators at variable loads. It can also divide the loads between generators if they work in parallel. This helps in the drop of the voltage. This results in the generator’s efficient response to the overloads. Put, it takes variable voltage ranges as input and outputs a fixed voltage.

What is an error voltage in a generator?

An error voltage is a difference between the actual voltage and the reference voltage.

An amplifier and an exciter provide at the receiving end of the voltage. The error voltage reaches the amplifier. It then amplifies the error voltage and supplies it to the exciter.

The exciter output control adjusts the fluctuation of the voltage in the alternator.

What is the importance of Automatic Voltage Regulators in a Generator?

The automatic voltage regulator maintains a constant voltage in a generator. If the voltage is not held, the performance of the generator might get affected.

The utilities, equipment, and machinery powered by the generator can stutter. Because due to unregulated voltage, a spark can occur.

The Automatic Voltage Regulator ensures the appliances' longevity as it guarantees that the load current is consistent. This helps in eliminating the damage caused by fluctuations.

Generators without regulators fail to meet the power requirements. Because due to upregulation, the voltage cannot be proper distributed among the appliances. So when the load requirements increase, the terminal voltage decreases with time.

What are the functions of the Automatic Voltage Regulator?

The main functions of AVR are as follows:

  1. It controls the voltage of the generator and stabilizes it.
  2. It operates as a machine to keep the steady-state stability of the voltage.
  3. It drops the high voltage by dividing the reactive load between parallel alternators (Alexander, 2016).
  4. The AVR controls the over-voltage that occurs due to the sudden loss of the load.
  5. It increases the excitation of the system under fault conditions.
  6. It ensures that a synchronizing power exists at the time of doing away with fault conditions.
  7. When the load changes, the AVR changes the excitation system’s load to keep the voltage the same.
  8. It operates in the exciter field. And adjusts the exciter output voltage and field current.
  9. During extreme fluctuations, it remains at peace and does not give a response. This way, the voltage remains steady and constant.

How to maintain an Automatic Voltage Regulator?

An AVR is a part of the alternator excitation system. While in operation, you should not remove the cover of the regulator. This can become dangerous for safety. The automatic voltage regulator requires maintenance after every 200 operational hours (Starpower, 2018).

The steps involved in maintenance are as follows:

  1. Remove the cover. Check if there’s any dirt or burned area on the surface. If there is, then clean it with a cloth. If the layer is not straight and flat, use sandpaper of 00 number. The sandpaper will help remove the attached dirt from the surface.
  2. Please turn to the connectors and check their fastness. Measure the resistance and value of each coil. If you see some damage, repair it. If the damage is beyond repair, replace it with new ones.
  3. See closing voltage, Reverse current and Limiting voltage. And limiting the current of the throttle through the interrupter. Then, look at the air gap of various contacts. Adjust them if they do not meet the standard requirements.
  4. Pay attention to the charging ammeter pointer when you start the generator. Check the adjusted regulator. Now
  5. When the engine operates, see if the ammeter pointer is pointing to the “-” side. Because when it operates at a moderate speed. The “–” would say that the current breaker contact is not disconnected. And the earthing switch should disconnect. If not done so, the battery, regulator, and charging generator would damage.
  6. See if the ammeter’s pointer points to “0” after the diesel engine starts to the rated speed. In that case, the change is not according to the technical requirements. So you should check this. Then adjust again as per the requirements given in the standard regulations chart. That paper comes along with the generator when you buy a new one.

The timely maintenance of the AVR ensures safe-level voltage change. Also, it will provide surge protection against electrical surges and generator overload. The maintenance sort-of helps in reinvigorating the energy of the generator. So this way, the AVR will better be able to prevent shorting and handle overloads. When needed. It will transfer the generators’ reactive loads if they connect in parallel. All these processes will be possible through efficient, effective, and timely maintenance.


We conclude that an Automatic Voltage Regulator is a crucial part of the generator. Without it, the generator is susceptible to power shortages and sparks. As in the absence of the AVR, the voltage would not remain stable. This instability can affect the performance of the generator.

So it would help if you always preferred a quality AVR. This will ensure that the generator runs for a long time: even the load or operating temperature changes. An AVR would protect the functioning from getting disrupted. And would give its best not to harm the electrical appliances attached to it.

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