It has apparently been used on only 5 questions. Two are for permanent-magnet motors and generators and one for a permanent-split-capacitor (PSC) motor.
I would be inclined to create permanent-magnet-motor and permanent-magnet-generator tags. A single permanent-magnet-machine tag might be better, but some people might not recognize it as meaning either a motor or a generator.
Would a permanent-split-capacitor-motor tag be too unwieldy? I suppose that anyone who would be looking for that might be just as likely to look for psc-motor. Perhaps the single-phase tag is all that is really needed, leaving the asker to give the sub-type as part of the description.