I would imagine those off the shelf motors are relatively cheap, but I do like the idea of variable control. Wonder if the compressor efficiency (from an air-producing standpoint) would decline as rpm dropped? ( more time for leakage as rpm decreases)Seems like it might be more of an issue for rotary compressors vs. piston, but then again as the cups and valves wore I would expect a loss there also.
Sometimes higher rpm can compensate for worn components. For a time, anyway.
I agree. The variable speed would definitely require a fixed displacement pump to make sense. Theoretically, when subjected to a constant load (back pressure), pump life for a fixed displacement pump is determined primarily by number of cycles. When parts start to wear, the motor would need to run faster to compensate for the loss in efficiency. The speed control input would either need to be pressure or flow.
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