The way I understand the governor of a synchronous generator is as follows:

As loads change on the system, the frequency will change. The governor's purpose is to maintain an approximately constant speed of rotation with varying loads. Once the desired speed i.e. frequency is set, the governor will compare the actual speed to the reference (i.e. set-point or desired) speed value, if they're not equal, the governor will change the amount of fuel flow (i.e., the generator output), so that a rise in speed will reduce the fuel intake and a fall in speed will increase it.

For a fixed load, the governor will be zero while the normal power supply continues to feed the constant load.

Once steady state is reached the governor output will become zero, but the generator continues to supply real power to the load at constant speed.

Is that correct?

  • \$\begingroup\$ Are we talking about a standalone synchronous generator? Because if it's working on a grid, the speed is shared among all generators in the grid. There's phase lag between the different generators at most. \$\endgroup\$
    – Janka
    Sep 23, 2021 at 12:34
  • \$\begingroup\$ "the governor will be zero while the normal power supply continues to feed the constant load", what's a normal power supply? What's the question, here? \$\endgroup\$ Sep 23, 2021 at 12:42
  • \$\begingroup\$ Here is good document you can read. \$\endgroup\$ Sep 23, 2021 at 13:13

1 Answer 1


The governor controls the RPM of the motor and generator. There are mechanical and electrical governors that control motor speed. In a gas-powered generator, the rate of fuel is increased to increase the motor and generator speed and keep the output frequency at the target. When the load increases more fuel is required to maintain the frequency. Without a governor system, the speed and frequency would decrease.

Speed controllers use a control loop to react to load changes. These loops generate an error signal that increases or decreases power to the motor to maintain the frequency. Depending on the type of loop, once steady state is reached, the error will either go to zero or to a fixed value to keep the speed within range.


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