Paul, the FAA uses mag-amps for speed control of the TACAN antenna motors. 5HP, 3 phase, 900 RPM (+/- not very much variation). Generally, they run forever and ever....with no thought to anything but cooling. Dave Dunsmoor > Has anyone here ever used magnetic amplifiers? If so, what did/do you think > about them? > > > Paul Gray, N0JAA > Satellite Beach, FL