# US 9,438,146 B2 · Reducing the power consumption of a brushless motor > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,438,146 B2 - Document ID: US9438146B2 - Status: Granted - Kind: B2 - Application number: 14/304,441 - 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: Tuncay Celik; Libo Zheng - Web page: https://patentgrep.com/patent/US9438146B2 ## CPC - H02P 6/28: Arrangements for controlling current (H02P6/10 takes precedence) - H02P 6/15: Controlling commutation time - H02P 29/60: Controlling or determining the temperature of the motor or of the drive (H02P29/02 takes precedence) - 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 motor. The method includes measuring a temperature of the motor, adjusting a control value in the event that the measured temperature is lower than a threshold, and exciting a winding of the motor. The control value is then used to define an attribute of excitation, and the adjustment to the control value reduces the input power of the motor. ## Claims ### Claim 1 A method of controlling a brushless motor, the method comprising: measuring a temperature of the motor; adjusting a control value in the event that the measured temperature is lower than a threshold; and exciting a winding of the motor, wherein the control value is used to define an attribute of excitation, and the adjustment to the control value reduces the input power of the motor. ### Claim 2 (depends on 1) The method of claim 1, wherein the control value is adjusted such that the input power of the motor is reduced by a larger amount in response to a lower measured temperature. ### Claim 3 (depends on 2) The method of claim 2, wherein adjusting the control value comprises applying a compensation value to the control value, the compensation value is temperature dependent, and a larger compensation value is applied to the control value in response to a lower temperature such that the reduction in the input power is larger. ### Claim 4 (depends on 3) The method of claim 3, wherein the method comprises storing a temperature lookup table that comprises a compensation value for each of a plurality of temperatures, and indexing the temperature lookup table using the measured temperature to select the compensation value. ### Claim 5 (depends on 1) The method of claim 1, wherein the method comprises adjusting the control value such that the difference between the input power of the motor at the measured temperature and the input power of the motor at the threshold temperature is smaller when the control value is adjusted. ### Claim 6 (depends on 1) The method of claim 1, wherein the input power of motor at the threshold temperature is A, the input power of the motor at the measured temperature when the control value is adjusted is B, the input power of the motor at the measured temperature when the control value is not adjusted is C, and the method comprises adjusting the control value such that |A−B|<|A−C|. ### Claim 7 (depends on 1) The method of claim 1, wherein the input power of motor at the threshold temperature is A, the input power of the motor at the measured temperature when the control value is adjusted is B, and the method comprises adjusting the control value such that difference between A and B is no more than 1% of A. ### Claim 8 (depends on 1) The method of claim 1, wherein the method comprises adjusting the control value in the event that the measured temperature is within a range of temperatures spanning at least 40 deg C. ### Claim 9 (depends on 1) The method of claim 1, wherein the method comprises employing a threshold that depends on the speed of the motor. ### Claim 10 (depends on 9) The method of claim 9, wherein the method comprises employing a higher threshold in response to a higher motor speed. ### Claim 11 (depends on 1) The method of claim 1, wherein the control value is adjusted such that the input power of the motor is reduced by a larger amount in response to a higher motor speed. ### Claim 12 (depends on 11) The method of claim 11, wherein adjusting the control value comprises applying a compensation value to the control value, the compensation value depends on the speed of the motor, and a larger compensation value is applied to the control value in response to a higher motor speed such that the reduction in the input power is larger. ### Claim 13 (depends on 12) The method of claim 12, wherein the method comprises storing a temperature lookup table that comprises a compensation value for each of a plurality of motor speeds, measuring the speed of the motor, and indexing the temperature lookup table using the measured motor speed to select the compensation value. ### Claim 14 (depends on 1) The method of claim 1, wherein the control value defines the phase or the length of excitation. ### Claim 15 (depends on 14) The method of claim 14, wherein the method comprises exciting the winding at times relative to zero-crossings of back EMF or rising inductance in the winding by a phase period, and exciting the winding for a conduction period, and the control value defines the phase period or the conduction period. ### Claim 16 (depends on 1) The method of claim 1, wherein the method comprises dividing each half of an electrical cycle of the motor into a conduction period followed by freewheel period, and the control value defines one of a phase and a length of the conduction period. ### Claim 17 (depends on 1) The method of claim 1, wherein the motor comprises a rotor having a permanent magnet, and the measured temperature is proportional to the temperature of the magnet. ### Claim 18 A method of controlling a brushless motor, the method comprising: storing a power lookup table, the power lookup table comprising a control value for each of a plurality of voltages or speeds; measuring the magnitude of a supply voltage or the speed of the motor; indexing the power lookup table using the measured voltage or speed to select a control value; measuring a temperature of the motor; applying a compensation value to the selected control value in the event that the measured temperature is lower than a threshold; and exciting a winding of the motor with the supply voltage, wherein the selected control value defines an attribute of excitation, and the compensation value when applied to the selected control value reduces the input power of the motor. ### Claim 19 A method of controlling a brushless motor, the method comprising: storing a power lookup table, the power lookup table comprising a control value for each of a plurality of voltages or speeds; storing a temperature lookup table, the temperature lookup table comprising a compensation value for each of a plurality of temperatures; measuring the magnitude of a supply voltage or the speed of the motor; measuring a temperature of the motor assembly; indexing the power lookup table using the measured voltage or speed to select a control value; indexing the temperature lookup table using the measured temperature to select a compensation value; applying the selected compensation value to the selected control value to obtain a temperature-compensated control value; and exciting a winding of the motor with the supply voltage, wherein the temperature-compensated control value is used to define an attribute of excitation. ### Claim 20 (depends on 19) The method of claim 19, wherein the temperature lookup table comprises compensation values that when applied to the selected control value ensure that the input power of the motor at the measured voltage or speed point is substantially the same across a range of temperatures. ### Claim 21 (depends on 20) The method of claim 20, wherein the range of temperatures spans at least 40 deg C. ### Claim 22 A control circuit for controlling a brushless motor, the control circuit being configured to: measure a temperature of the motor; adjust a control value in the event that the measured temperature is lower than a threshold; and excite a winding of the motor, wherein the control value is used to define an attribute of excitation, and the adjustment to the control value reduces the input power of the motor. ### Claim 23 (depends on 22) The control circuit of claim 22, wherein the control circuit is included in a motor assembly for a brushless motor. ### Claim 24 (depends on 23) The control circuit of claim 23, wherein a compressor comprises an impeller and the motor assembly including the control circuit, and the impeller is driven by the motor assembly and generates an airflow that cools the motor assembly. ### Claim 25 A control circuit for controlling a brushless motor, the control circuit being configured to: store a power lookup table, the power lookup table comprising a control value for each of a plurality of voltages or speeds; store a temperature lookup table, the temperature lookup table comprising a compensation value for each of a plurality of temperatures; measure the magnitude of a supply voltage or the speed of the motor; measure a temperature of the motor assembly; index the power lookup table using the measured voltage or speed to select a control value; index the temperature lookup table using the measured temperature to select a compensation value; apply the selected compensation value to the selected control value to obtain a temperature-compensated control value; and excite a winding of the motor with the supply voltage, wherein the temperature-compensated control value is used to define an attribute of excitation. ### Claim 26 (depends on 25) The control circuit of claim 25, wherein the control circuit is included in a motor assembly for a brushless motor. ### Claim 27 (depends on 26) The control circuit of claim 26, wherein a compressor comprises an impeller and the motor assembly, and the impeller is driven by the motor assembly and generates an airflow that cools the motor assembly.