# Electrical Generator Q

1. Jan 24, 2012

### daredevil

Hi,

I was having some confusion understanding how the three phase generator works.

As far as I know AC is connected to the stator and DC is connected to the rotor and the changing magnetic field in the stator causes the rotor to rotate.

I was wondering what causes the rotor to rotate in one direction and how much AC current have to be supplied to the stator. I mean as the direction of AC is changing, the direction the rotor is rotating should also change, right

And, what is the total voltage of the three phase supply if a single phase is 240V.

2. Jan 24, 2012

### kunguz

Please see synchronous machine principles from:

http://www.google.com.tr/url?sa=t&r...9q7BiZFkA&sig2=LCIQGsbcJsqDKQm2o2qUWA&cad=rja

3. Jan 25, 2012

### gsal

Yeah, you could do some reading as recommended.

Other than that, I should say that in a generator, you do NOT connect electricity to the stator to make the rotor rotate...that's a motor!

A generator generates electricity and makes it come out of the stator terminals...a generator is kind of a transducer that converts mechanical energy into electrical energy. In a generator, the rotor rotates and as it is excited and has it own magnetic field, these two things ( mag field and motion) produce a voltage on the stator.

In a Y-connected generator, the phase to phase voltage is sqrt(3) that of a single phase.

4. Jan 27, 2012

### daredevil

Thanks..

So what causes the rotor to rotate in the generator if no current is connected to the stator

5. Jan 27, 2012

### gsal

Well, generators are typically installed at a power plant where there is a source of energy that can be used to rotate the rotor of the generator.

For example, where there is a big river with a lot of water, people build dams and a hydroelectric plant, where the water comes down and moves the blades of a turbine, which in turn moves the rotor of the generator.

Or, in a steam plant...a train comes around with a lot of coal, they burn the coal inside a boiler with a lot of water pipes...as the water heats up, they keep it pressurized and then they shot it into the blades of a steam turbine's blades, again, the turbine turns and as it is connected to the same shaft of the generator rotor, well, it turns it too.

etc., etc., etc.. geothermal plants, nuclear plants, some solar plants...they all first need to use some source of energy to move a turbine, then they connect a generator to the same shaft.

So, a turbine is a device that converts some kind of source energy into a rotational mechanical energy, a generator is a device that converts mechanical rotational energy into electricity and a motor is a device that converts electrical energy into mechanical rotational energy.

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