# Alternator for thermal generator (Coal-fired generator)

1. Oct 16, 2014

### Haewigh

I am doing a project on coal fired generator and I don't really
know how my Alternator will work. I'm currently trying to use a
2 pole stator, 5 former making 1 pole, single phase alternator.
These are the problems :
how do I calculate/obtain the power rating of my alternator/
generator
does the Alternator work like the dynamo that generate voltage
proportional to the rpm
does a 50Hz alternator operate at 3000rpm to generate 240v
relationship between torque, rpm and voltage

2. Oct 18, 2014

### Baluncore

Haewigh, welcome to PF.

Yes. An alternator produces a frequency directly determined by shaft RPM.

Yes. An alternator produces a voltage determined by RPM multiplied by rotor field strength.

So you will run the alternator at 3000 RPM to get a 3000 / 60 = 50Hz output.
You will need to adjust the DC field current to set the voltage at 240VAC (RMS).
Note that the world standard is now 230V AC, not 240VAC.
The DC field current passes through the slip-rings to the field winding on the rotor.

The maximum power will then be the AC current generated, multiplied by the 240VAC output voltage.
The thickness and so the resistance of the wire in the alternator will decide the average AC current that can be safely generated. If you draw greater current then the windings will get hot and their insulation will probably fail.

Power is torque multiplied by RPM. The torque will be proportional to power generated, since RPM is fixed to generate 50Hz.

http://en.wikipedia.org/wiki/Alternator