I have a design having an emagnet for a stator and a permanent magnet for the rotor. The question I have is, when applying current to the emagnet such as to create a N pole, the total attraction to the rotor (S) is a combination of the electric field generated by the emagnet, plus the attraction of the permanent magnet to just the steel core of the emagnet. However, when changing polarity of the emagnet, such that it is S, the repulsion to the permanent magnet (S) is only due to the fields created by the current flowing in the emagnet. The steel core does not play a part. With a strong enough permanent magnet, I can get it to attract to the emagnets steel core regardless of what the polarity happens to be or how much current I am applying. How do I balance current in the emagnet and the strength of the permanent magnet, so as to attain relatively equal push and pull with a polarity change to the emagnet. Hope you can follow that.
First, let me state that I am not an electrical engineer; but, I have worked with and designed some control systems so here are my thoughts on your issue. As I see it the only way to achieve your goal is with a half wave rectified input to your emagnet and the best type would be a square wave input. Using a half wave standard sine wave AC input will result in an inbalance of forces since when the clipped wave portion will result in a full half cycle attraction by the permanent magnet while the half sine wave input will only be fully balanced at its RMS value period. I hope this info is at least a bit helpful.
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