Magnetic bearing controller

• US 6,346,757 B1
• Filed: 07/12/2000
• Issued: 02/12/2002
• Est. Priority Date: 02/12/1998
• Status: Expired due to Fees

• Current Assignee: Ebara Corporation
• Original Assignee: Ebara Corporation
• Inventors: Shinozaki, Hiroyuki
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): Lam, Thanh
• Application Number:
  US09/600,116
• Time in Patent Office: 580 Days
• Field of Search: 310/90.5, 318/606, 318/607, 364/508, 333/167, 333/175, 333/176
• US Class Current: 310/90.5
• CPC Class Codes: F16C 2300/62 low pressure, e.g. elements operating under vacuum conditions
• CPC Class Codes: F16C 32/0451 Details of controllers, i.e. the units determining the power to be supplied, e.g. comparing elements, feedback arrangements with P.I.D. control
• CPC Class Codes: F16C 32/0457 Details of the power supply to the electromagnets

Abstract

It is an object of the present invention to provide a magnetic bearing controller which is able to levitate the controlled object stably by using controlled magnetic forces. In the magnetic bearing controller which supplies a controlled current to an electromagnet for levitating a rotating body at a predetermined position, the controller is provided with an eliminator unit for eliminating frequency components of frequency area which is used by the status detector unit. The eliminator unit is inserted between signal amplifier unit and power amplifier unit for generating controlled current.

Claims

1. A magnetic bearing device for levitating a rotating body at a predetermined position, said device comprising:

an electromagnet for generating magnetic force by a controlled current;

a power amplifier unit for supplying said controlled current to said electromagnet, said controlled current being pulse width modulated;

a signal amplifier unit for amplifying signal before inputting to said power amplifier; and

a status detector unit for detecting a status of said rotating body;

wherein said status detector unit uses a modulated signal of a certain fundamental frequency and an eliminator is inserted between said signal amplifier unit and said power amplifier unit for eliminating frequency components of a frequency area around said fundamental frequency.

2. A magnetic bearing device according to claim 1, wherein said power amplifier unit is provided with a pulse width modulation circuit which comprises a comparator for comparing an input signal with a chopper wave signal, and said eliminator is connected at a front end of said comparator.

3. A magnetic bearing device according to claim 1, wherein said status detector is an inductance type displacement sensor.

4. A magnetic bearing device according to claim 1, wherein said eliminator is a band eliminator filter.