# Does the rotation speed of a synchronous machine affect the voltages induced?

We know that synchronous generator are the go to for power generation. They essentially need an excitation current for the rotor and an external force to rotate it. This would induce a voltage in the 3 stator windings that has a frequency proportional to its rotation speed. The thing that I don't really understand is how do these machines produce a voltage amplitude that is independent of its rotation speed while Faraday's law clearly states that the EMF produced is dependant on the rate of variation of the flux. (So let say, I increase the rotation speed consequently the frequency will increase but will that affect my voltage?) Additionally, how do these generator provide sine waves, wouldn't that require a variation of the number of wire turns in each slot of the stator?

Thank you :)

• Voltage is induced, not current. – Andy aka Jan 17 '19 at 12:51
• True but I was assuming that the generator was loaded so this created a flowing current. Anyways, I edited my post to avoid confusion. Thanks :) – Ivan Bruski Jan 18 '19 at 20:24

They produce sine waves because they are rotating at a constant angular velocity. The induced voltage changes as $$\\cos(\theta)\$$ (Faraday’s law).