| 摘要 |
PROBLEM TO BE SOLVED: To provide a magnetic bearing vacuum pump in which open circuit of a sensor can be detected even if both of a pair of displacement sensors are open-circuited.SOLUTION: In a magnetic bearing vacuum pump in which the difference value of sensor signals from a pair of inductance displacement sensors 27p, 27m is determined by means of a differential amplifier 502, and an electromagnet current is controlled based on the differential output therefrom, a carrier signal having an amplitude Vinp is applied to a series circuit of the displacement sensor 27p and a resistor Rdp, and a carrier signal having an amplitude Vinm, different from the amplitude Vinp, is applied to a series circuit of the displacement sensor 27m and a resistor Rdm. As a result, the differential output is different from zero when both displacement sensors 27p, 27m are open-circuited, and can be distinguished from the case where a rotor shaft 30a is levitated magnetically at a central position (differential output=0), and open circuit of both sensors can be detected. |
