High efficiency drive circuit for an active magnetic bearing system
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United States of America Patent
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-
May 6, 1997
Grant Date -
N/A
app pub date -
Oct 28, 1994
filing date -
Oct 28, 1994
priority date (Note) -
In Force
status (Latency Note)
Importance
Abstract
A plurality of electromagnetics in an array surround a shaft, with current controlled in the coils of the electromagnets to support the shaft at a desired position approximately centered between the electromagnets. Shaft position sensors provide feedback to a control system for modulating the current to the electromagnet coils, which are arranged in pairs on opposite sides of the shaft. A drive circuit for each coil includes first and second switching transistors which connect the coil to the power supply to transfer a current pulse to the coil. A pair of circulating diodes begin conducting when the transistors turn off, and return power to the supply. A control circuit for the drive circuits interleaves on and off intervals for the coils in the electromagnet pairs so that one coil of the pair is being switched off at about the same time as the other coil of the pair is being switched on. The result is that the energy being returned to the power supply by the off-turning coil is diverted, at least in part, to the on-turning coil, thereby to reduce net current drain from the power supply.
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