Electromagnetic support with unilateral control currents

Details Electromagnetic support with unilateral control currents Electromagnetic support with unilateral control currents

1991-03-04

1993-11-23

Gaffin, Jeffrey A.

Electricity: electrical systems and devices

Control circuits for electromagnetic devices

Systems for magnetizing, demagnetizing, or controlling the...

310 905, H02N 1500

Patent

active

052649822

ABSTRACT:
A device for positioning a body (5) by means of at least one pair of electromagnets (13, 15). A position sensor (29) measures the size of an air gap (23) between one of the electromagnets (13, 15) and a guide beam (1). An output signal of the position sensor (29) is applied to an electronic control unit (35) which passes a control current through the electromagnets (13, 15) in dependence on a difference between the measured and a desired size of the air gap (23). In one embodiment an electrical switch (53) is connected between the control unit (35) and the two electromagnets (13, 15) controlled by the control unit (35), applying the control current to only one of the two electromagnets (13, 15) in dependence on the polarity of a control signal from the control unit (35). The use of the switch insures that the control current flows through only one of the two electromagnets at a time so that in a simple manner a difference necessary for supporting the body is achieved between the forces exerted on the guide beam (1) by the electromagnets (13, 15). the electrical resistance losses in the electromagnets (13, 15) in such a device are low, the device is eminently suitable for use as an electromagnetic bearing in an optical lithographical device for the irradiation of semiconductor substrates, or in other precision machines.

REFERENCES:
E. M. H. Kamerbeek, "Magnetic Bearings", Philips Technical Review, vol. 41, No. 11/12, 1983/84, pp. 348-361.

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