CONTROLLER FOR MAGNETIC BEARING

PURPOSE:To maintain the extent of good control over a turning shaft by installing a comparator, and when the turning shaft is largely displaced and a detecting signal exceeds the setting value, outputting a specified level signal, giving it to the comparator so as to be added or subtracted between a phase compensator and a power amplifier while adding or subtracting an exciting current for an electromagnet. CONSTITUTION:When a turning shaft 21 has largely come nearer to the side of an electromagnet 22b, a detecting signal S1 of a detector 23 turns to a signal S1' of its component exceeding the setting amplitude by an amplitude limiter 24, and also turns to a displacement signal S3' by way of a phase compensator 28. A comparator 34 outputs a level L signal S7 while the detecting signal S1 exceeds an upper limit value SUTP by an setting value signal S6 and arrives at the lower limit value SLTP, and it is added to the displacement signal S3' by an add circuit 29. With this constitution, control signals S5a', S5b' being given to power amplifiers 32a, 32b are subjected to addition or subtraction, so that magnetic attraction of the electromagnets 22a, 22b is increased or decreased correspondingly, thus the turning shaft 21 receives the large attraction and is reset to the specified position.