Quote:
Originally Posted by MPaulHolmes
I was just trying to understand when a 3 phase induction motor acts like a generator. My thinking was, if it somehow acted like a generator while hooked up to the AC controller, it would be a good opportunity to test the simulated grid tie feature.
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The controller needs to supply the excitation for the field ... as well as the initial 'kick' for real power to get current flow through the rotor.
Back to basic principles - As you know, current cutting through the magnetic flux causes torque in motoring mode. The controller or the grid supplies the rotating magnetic flux .. so the rotor is still 'rotating' through the flux even when it is standing still.
... so pushing or turning (torque) the rotor through the magnetic flux causes current flow in generating mode. That works in a Permanent magnet generator without any power required for a start. For the electromagnets in the stator, you need electricity to 'start off' the generator. The self-exciting home generators have small permanent magnets in the stator somewhere ... or use a capacitor/battery combination ...