Generator Windings 3

[rockman7892]

I was involved in the startup of a 480V generator over the last few days and used it as an opportunity to learn more about how generators work.

The one question I cant seem to figure out about the generator that I have is why there are two sets of windings on each of the ouput phases as shown no the attached drawing. Why are there two sets of windings connected in series for each phase as opposed to one winding?

Also the generator exication was rated at 32V and 7.2A. Does this mean that the voltage regulator outputs 7.2A DC to the field coils in the rotor? Will varying this 7.2A output change the output voltage of the generator?

 

[rbulsara]

or in other words, maximum unity pf load you can have is equal to the kW rating of the machine.

 

[waross]

I thought that I said this but it may have been in another thread;
Dropping the voltage does not increase the current of a resistive load.
You can test the prime mover with a resistive load of 750 kW.
The KVA rating is a reflection of the heating of the set caused by the load current. It is rated Amps times Rated Voltage (Of the generator end only, not the complete set.)
So, at 480 Volts, the rated current will be:
750 kW / 0.8 = 937.5 KVA
937.5 KVA at 480 Volts three phase will be 1128 amps. So far so good.
Now, if you drop the voltage to 480 V x 0.8 = 384 Volts and load the set up to 1128 Amps, you will have a load of 750 Kw.
Your prime mover will not be overloaded and you will be able to verify that the set can deliver 1128 amps without overheating or tripping the protection.
This will cover most of the issues that you want to test on a set in that size range.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[rockman7892]

Would dropping the voltage increase the current if there were reactive loads involved?