# US 10,371,159 B2 · Magnetic bearing device, and vacuum pump having same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,371,159 B2 - Document ID: US10371159B2 - Status: Granted - Kind: B2 - Application number: 14/783,740 - Filed: 2014-03-07 - Published: 2016-09-01 - Granted: 2019-08-06 - Earliest claimed: 2013-04-16 - Assignees: Edwards Japan Limited - Applicants: Edwards Japan Limited - Inventors: Toshiaki Kawashima - Web page: https://patentgrep.com/patent/US10371159B2 ## CPC - F04D 29/058: magnetic; electromagnetic - 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} - F16C 32/0455: {including digital signal processing [DSP] and analog/digital conversion [A/D, D/A]} - F16C 32/0457: {Details of the power supply to the electromagnets} - H02K 7/09: with magnetic bearings - H02K 7/14: Structural association with mechanical loads, e.g. with hand-held machine tools or fans (with fan or impeller for cooling the machine H02K9/06) - F04D 19/042: {Turbomolecular vacuum pumps} - F16C 32/0489: {with active support of five degrees of freedom, e.g. two radial magnetic bearings combined with an axial bearing} - F16C 2360/45: Turbo-molecular pumps - F04D: NON-POSITIVE-DISPLACEMENT PUMPS (engine fuel-injection pumps F02M; ion pumps H01J41/12; electrodynamic pumps H02K44/02) - F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) ## Abstract An object of the present invention is to provide a magnetic bearing device designed to achieve reduction in cost and size of a circuit by omitting a DC/DC converter that has been used for obtaining a control power voltage of a magnetic bearing, and to provide a vacuum pump having the magnetic bearing device. The magnetic bearing device has: position detection means for detecting a radial position and an axial position of a rotor; magnetic bearing means for controlling the radial position and the axial position with an electromagnet based on the radial position and the axial position detected by the position detection means; an excitation circuit that includes a switching element for connecting/disconnecting between the electromagnet and a power supply; electromagnetic current detection means for detecting a signal of a current flowing through the electromagnet; power supply voltage detection means for detecting a signal of a voltage of the power supply; and pulse width calculation means for calculating, at each timing, a pulse width for operating pulse control for the switching element. The pulse width is calculated based on the voltage of the power supply detected by the power supply voltage detection means and the current detected by the electromagnetic current detection means. ## Claims ### Claim 1 A magnetic bearing device, comprising: a rotor; position detection means for detecting a radial position or an axial position of the rotor; magnetic bearing means for controlling the radial position or the axial position with an electromagnet; an excitation circuit that includes a switching element for connecting and disconnecting the electromagnet and a power supply; electromagnetic current detection means for detecting a current flowing through the electromagnet; power supply voltage detection means for detecting a voltage of the power supply; and pulse width calculation means for calculating, at each timing, a pulse width for operating pulse control for the switching element, wherein the pulse width calculation means calculates the pulse width based on the voltage detected by the power supply voltage detection means and the current detected by the electromagnetic current detection means to correct a fluctuation of the voltage of the power supply. ### Claim 2 (depends on 1) The magnetic bearing device according to claim 1, further comprising correction calculation means for: calculating a first correction based on a current error between a current value of the current detected by the electromagnetic current detection means and a current command value, calculating a second correction based on the pulse width at the present, and calculating a third correction based on a voltage drop caused by a resistive component of the electromagnet, wherein errors of DC components that are included in the third correction and the second correction are corrected by integration. ### Claim 3 (depends on 1) The magnetic bearing device according to claim 1, wherein a switching frequency for connecting and disconnecting the switching element of the excitation circuit is an even multiple of a carrier frequency of the position detection means. ### Claim 4 A magnetic bearing device, comprising: a rotor; position detection means for detecting a radial position or an axial position of the rotor; magnetic bearing means for controlling the radial position or the axial position with an electromagnet; an excitation circuit that includes a switching element for connecting/disconnecting between the electromagnet and a power supply; electromagnetic current detection means for detecting a current flowing through the electromagnet; power supply voltage detection means for detecting a voltage of the power supply; pulse width calculation means for calculating, at each timing, a pulse width for operating pulse control for the switching element; a first rectifier element connecting a first end of the electromagnet to a negative electrode of the power supply; and a second rectifier element connecting a second end of the electromagnet to a positive electrode of the power supply, wherein the pulse width is calculated based on the voltage detected by the power supply voltage detection means and the current detected by the electromagnetic current detection means, wherein the switching element is configured by a first switching element connecting the first end of the electromagnet to a positive electrode of the power supply and a second switching element connecting the second end of the electromagnet to a negative electrode of the power supply; and wherein the electromagnetic current detection means is disposed on a ground side of the second switching element. ### Claim 5 (depends on 1) The magnetic bearing device according to claim 1, wherein the electromagnetic current detection means consists of at least a resistive element and a differential amplifier, voltages of both ends of the resistive element, which are generated as a result of a voltage drop of the resistive element caused by the current flowing through the electromagnet, are input to the differential amplifier, and the current flowing through the electromagnet is detected based on an output voltage of the differential amplifier. ### Claim 6 (depends on 1) The vacuum pump comprising the magnetic bearing device according to claim 1. ### Claim 7 (depends on 2) The magnetic bearing device according to claim 2, wherein a switching frequency for connecting and disconnecting the switching element of the excitation circuit is an even multiple of a carrier frequency of the position detection means. ### Claim 8 (depends on 2) The magnetic bearing device according to claim 2, wherein the electromagnetic current detection means consists of at least a resistive element and a differential amplifier, voltages of both ends of the resistive element, which are generated as a result of a voltage drop of the resistive element caused by the current flowing through the electromagnet, are input to the differential amplifier, and the current flowing through the electromagnet is detected based on an output voltage of the differential amplifier. ### Claim 9 (depends on 3) The magnetic bearing device according to claim 3, wherein the electromagnetic current detection means consists of at least a resistive element and a differential amplifier, voltages of both ends of the resistive element, which are generated as a result of a voltage drop of the resistive element caused by the current flowing through the electromagnet, are input to the differential amplifier, and the current flowing through the electromagnet is detected based on an output voltage of the differential amplifier. ### Claim 10 (depends on 7) The magnetic bearing device according to claim 7, wherein the electromagnetic current detection means consists of at least a resistive element and a differential amplifier, voltages of both ends of the resistive element, which are generated as a result of a voltage drop of the resistive element caused by the current flowing through the electromagnet, are input to the differential amplifier, and the current flowing through the electromagnet is detected based on an output voltage of the differential amplifier. ### Claim 11 (depends on 4) The magnetic bearing device according to claim 4, wherein the electromagnetic current detection means consists of at least a resistive element and a differential amplifier, voltages of both ends of the resistive element, which are generated as a result of a voltage drop of the resistive element caused by the current flowing through the electromagnet, are input to the differential amplifier, and the current flowing through the electromagnet is detected based on an output voltage of the differential amplifier. ### Claim 12 (depends on 2) A vacuum pump comprising the magnetic bearing device according to claim 2. ### Claim 13 (depends on 3) A vacuum pump comprising the magnetic bearing device according to claim 3. ### Claim 14 (depends on 6) A vacuum pump comprising the magnetic bearing device according to claim 6. ### Claim 15 (depends on 4) A vacuum pump comprising the magnetic bearing device according to claim 4. ### Claim 16 (depends on 5) A vacuum pump comprising the magnetic bearing device according to claim 5. ### Claim 17 (depends on 8) A vacuum pump comprising the magnetic bearing device according to claim 8. ### Claim 18 (depends on 9) A vacuum pump comprising the magnetic bearing device according to claim 9. ### Claim 19 (depends on 10) A vacuum pump comprising the magnetic bearing device according to claim 10. ### Claim 20 (depends on 11) A vacuum pump comprising the magnetic bearing device according to claim 11.