What does 'rated voltage' we see written on the name plate of synchronous machines mean? Is it the generated voltage or terminal voltage? By generated voltage I mean the EMF induced in the machine and by terminal voltage I mean the voltage obtained after considering the synchronous impedance.
Why am I confused?
Consider the synchronous machine as generator. If I consider rated voltage to be generated, voltage produced when rotor rotates at rated speed then what about the field current? Since induced voltage also depends upon field current, we may obtain different values for generated voltage if we vary field current. So for which value of field current is rated voltage printed on machine if generated voltage is actually the rated voltage in first place?
Coming to considering the rated voltage as terminal voltage... I can hardly get my head around with this case. How can we fix the terminal voltage? It will vary as we vary the load. For example, a DC battery rated as 9 volts means that the generated voltage in the battery is 9 volts and as you vary the load across the battery, the terminal voltage will subsequently also vary.
The same thing is when I consider the synchronous machine as a motor.
What does the rated voltage of a synchronous machine mean?