# US 9,438,150 B2 · Method of controlling a brushless permanent-magnet motor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,438,150 B2 - Document ID: US9438150B2 - Status: Granted - Kind: B2 - Application number: 14/304,599 - Filed: 2014-06-13 - Published: 2014-12-18 - Granted: 2016-09-06 - Earliest claimed: 2013-06-13 - Assignees: Dyson Technology Limited - Applicants: Dyson Technology Limited - Inventors: Libo Zheng; Yongji Zhou; Tuncay Celik - Web page: https://patentgrep.com/patent/US9438150B2 ## CPC - H02P 6/157: {wherein the commutation is function of electro-magnetic force [EMF]} - H02P 29/10: for preventing overspeed or under speed - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS ## Abstract A method of controlling a brushless permanent-magnet motor. The method includes commutating a winding of the motor at times relative to zero-crossings of back EMF in the winding. Commutation is then advanced when the motor operates over a first speed range, and commutation is retarded when the motor operates over a second speed range higher than that of the first speed range. ## Claims ### Claim 1 A method of controlling a brushless permanent-magnet motor, the method comprising commutating a winding of the motor at times relative to zero-crossings of back EMF in the winding, wherein commutation is advanced when the motor operates over a first speed range, commutation is retarded when the motor operates over a second speed range, and the second speed range is higher than the first speed range. ### Claim 2 (depends on 1) The method of claim 1, wherein the second speed range has a minimum greater than 50 krpm. ### Claim 3 (depends on 1) The method of claim 1, wherein the second speed range spans at least 5 krpm. ### Claim 4 (depends on 1) The method of claim 1, wherein the method comprising retarding commutation by a retard period when the motor operates over the second speed range, and varying the retard period in response to changes in a supply voltage used to excite the winding or the speed of the motor. ### Claim 5 (depends on 4) The method of claim 4, wherein the method comprises increasing the retard period in response to an increase in the supply voltage or a decrease in the speed of the motor. ### Claim 6 (depends on 1) The method of claim 1, wherein the method comprises sequentially exciting and freewheeling the winding over each electrical half-cycle when operating over the first speed range, the winding being freewheeled when current in the winding exceeds a predefined limit, and dividing each electrical half-cycle into a conduction period followed by a freewheel period when operating over the second speed range, the winding being excited during the conduction period and freewheeled during the freewheel period. ### Claim 7 (depends on 6) The method of claim 6, wherein the method comprises dividing the conduction period into a first excitation period, a further freewheel period and a second excitation period, the winding is excited during each excitation period and the winding is freewheeled during the further freewheel period. ### Claim 8 (depends on 1) The method of claim 1, wherein commutation is advanced when the motor operates over a third speed range, and the third speed range is higher than the second speed range. ### Claim 9 (depends on 8) The method of claim 8, wherein the method comprises dividing each electrical half-cycle of the motor into a conduction period followed by a freewheel period when operating over the second speed range and the third speed range, the winding being excited during the conduction period and freewheeled during the freewheel period. ### Claim 10 (depends on 8) The method of claim 8, wherein the method comprises driving the motor at constant power over the second speed range and driving the motor at a constant power over the third speed range, and the power of the motor over the second speed range is lower than that over the third speed range. ### Claim 11 (depends on 8) The method of claim 8, wherein the second speed range and the third speed range each span at least 5 krpm. ### Claim 12 (depends on 1) The method of claim 1, wherein commutation is synchronised when the motor operates over a fourth speed range, and the fourth speed range is lower than the first speed range. ### Claim 13 A method of controlling a brushless permanent-magnet motor, the method comprising commutating a winding of the motor at times relative to zero-crossings of back EMF in the winding, wherein commutation is advanced when the motor operates over a first speed range and when the motor operates over a third speed range, commutation is retarded when the motor operates over a second speed range, the second speed range is higher than the first speed range, and the third speed range is higher than the second speed range. ### Claim 14 A method of controlling a brushless permanent-magnet motor, the method comprising commutating a winding of the motor at times relative to zero-crossings of back EMF in the winding, wherein commutation is advanced when the motor operates over a first speed range, commutation is retarded when the motor operates over a second speed range, commutation is synchronised when the motor operates over a fourth speed range, the second speed range is higher than the first speed range, and the fourth speed range is lower than the first speed range. ### Claim 15 A control circuit for a brushless permanent-magnet motor, the control circuit being configured to commutate a winding of the motor at times relative to zero-crossings of back EMF in the winding, wherein commutation is advanced when the motor operates over a first speed range, commutation is retarded when the motor operates over a second speed range, and the second speed range is higher than the first speed range. ### Claim 16 (depends on 15) The control circuit of claim 15, wherein the control circuit is included in a motor assembly for a brushless permanent-magnet motor. ### Claim 17 A control circuit for a brushless permanent-magnet motor, the control circuit being configured to commutate a winding of the motor at times relative to zero-crossings of back EMF in the winding, wherein commutation is advanced when the motor operates over a first speed range and when the motor operates over a third speed range, commutation is retarded when the motor operates over a second speed range, the second speed range is higher than the first speed range, and the third speed range is higher than the second speed range. ### Claim 18 (depends on 17) The control circuit of claim 17, wherein the control circuit is included in a motor assembly for a brushless permanent-magnet motor. ### Claim 19 A control circuit for a brushless permanent-magnet motor, the control circuit being configured to commutate a winding of the motor at times relative to zero-crossings of back EMF in the winding, wherein commutation is advanced when the motor operates over a first speed range, commutation is retarded when the motor operates over a second speed range, commutation is synchronised when the motor operates over a fourth speed range, the second speed range is higher than the first speed range, and the fourth speed range is lower than the first speed range. ### Claim 20 (depends on 19) The control circuit of claim 19, wherein the control circuit is included in a motor assembly for a brushless permanent-magnet motor.