Why Do We Keep The Speed Of The Synchronous Generator Constant At No-Load? What Happens If The Speed Varies?
Synchronous generators are constant-speed motors. They work at the synchronous speed of the power supply.
They are commonly used for constant speed operation under idle conditions to improve power factor¹.
When a synchronous generator is running, something turns the rotor and something creates a magnetic field for the rotor.
The magnetic field rotates in the stator wires and creates a voltage.
If nothing is connected to the stator, this means that there is voltage in the stator but no current is flowing.
The voltage on the stator is an alternating voltage, but the stator is not only an alternating voltage but also like a battery on a shelf that does nothing other than be ready to supply current immediately when a load is connected².
In a permanent magnet synchronous generator, the no-load losses are losses due to friction, resistance (drift), reluctance torque, hysteresis, and eddy currents. A wound field synchronous generator has additional losses associated with producing field excitation.
Large machines can suffer additional losses from cooling, lubrication, monitoring, and safety systems².
When the speed changes, it causes changes in frequency and output voltage, which can be harmful to electrical equipment.