Three phase induction generator on a single phase supply

dec335; what sort of power source to drive the generator, gas engine, or electric motor? to dive it overspeed. perry

Perry,

I'm using a DC motor in the lab to drive it overspeed but eventually if the project works, it will be installed in a small hydro project.

Declan

Hang on. It started being driven from a single phase supply, now it's driven by a DC motor. Can the confusion go away, please?

I am trying to use a three phase induction machine to generate electricity that is connected to a single phase supply. I am currently doing work in the lab to get the setup running smoothly and then the machine will be installed in a small hydro project where three phase power in unavailable. I am using the DC machine in the lab to run the induction machine over synchronous speed so that it operates as a generator. I have also done testing in the lab with the induction machine running as a motor, driving a load and everything worked as expected as shown in my post above but it is not working well when it is running as a generator.

How do you expect a water wheel in a small hydro to run above synchronous speed? And how do you expect someone to offer job with a Masters but doesn't know if a synchronous generator is more efficient or an induction.

In simple terms, you do not have the ability to draw a CIRCLE DIAGRAM for the equipment otherwise this topic would not have been here in discussion (sorry to have said that).

While you are trying to support your thesis with impedance relationships without realizing that a machine has a working principle on which it works.

With single phase in conjunction with capacitor at motor terminals produces a phase shift to give rotating magnetic field across the rotor symmetrical to a three phase connection to the three phase motor windings.

When turned around as a generator the three phase motor windings have the inherent ability to produce the balanced desired results - effect of the capacitor across two of the terminals in this particular case is to cause considerable distortion of the output.

mountk2,

The generator does not have the ability to produce the balanced desired results as I have tried to run it without a capacitor across the phases and there is a massive imbalance in the phases which causes overheating.

Declan

I have to say that induction generator alone is incapable to supply a power system and therefore MUST ALWAYS operate in parallel with either synchronous machines or with a set of balanced capacitors.

As of reasoning it should be noted that the generator draws down all its excitation from the system and so must receive a definite amount of lagging kVA for a given voltage and load currents.

(For an induction generator the power factor of the output is fixed in value by the generator characterstics and is always LEADING, standing indipendent of the external circuit).