The high efficiency drive circuit null for the active magnetic bearing system

摘要

PROBLEM TO BE SOLVED: To reduce current drain from the power supply by efficiently using the power supply to a coil by turning on one of coils in turning off the other coil in modulation of a pair of coils arranged in a magnetic bearing. ;SOLUTION: Current in an electromagnetic coil of magnetic bearings 21, 22, 24 is modulated by a control circuit 70 and the modulation is executed by controlling the duty cycle of the voltage pulse fed to respective coils 30-33, 40-43, 50, 51. The control circuit 70, for example, interleaves on and off intervals for the coils 30, 31 in the electromagnet pairs so that one coil 31 of the pair is being switched off at about the same time as the other coil 30 of the pair is being switched on. As for the polarity of the circulating diodes in the drive circuit 61, the energy being returned from the off-turning coil 31 to the power supply 60 can be utilized for the on-turning coil 30, thereby reducing the net current drain from the power supply 60.;COPYRIGHT: (C)1996,JPO