# US 11,451,178 B2 · Motor drive operation at light load conditions > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,451,178 B2 - Document ID: US11451178B2 - Status: Granted - Kind: B2 - Application number: 17/210,297 - Filed: 2021-03-23 - Published: 2021-07-08 - Granted: 2022-09-20 - Earliest claimed: 2019-08-01 - Assignees: Lennox Industries Inc. - Applicants: Lennox Industries Inc. - Inventors: Jose Juan Sandoval - Web page: https://patentgrep.com/patent/US11451178B2 ## CPC - H02P 23/02: specially adapted for optimising the efficiency at low load - B60H 1/00428: {electric} - F24F 11/46: Improving electric energy efficiency or saving - H02P 27/085: {wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency} - B60H 2001/327: {related to a compressing unit} - F24F 2110/10: Temperature - F24F 2140/50: Load - F25B 49/022: {Compressor control arrangements} - F25B 2600/0253: with variable speed - F25B 2700/21171: of the fluid cooled by the evaporator - Y02T 10/88: Optimized components or subsystems, e.g. lighting, actively controlled glasses - H02P: CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS - B60H: ARRANGEMENTS OF HEATING, COOLING, VENTILATING OR OTHER AIR-TREATING DEVICES SPECIALLY ADAPTED FOR PASSENGER OR GOODS SPACES OF VEHICLES - F24F: AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING (removing dirt or fumes from areas where they are produced B08B15/00; vertical ducts for carrying away waste gases from buildings E04F17/02; tops for chimneys or ventilating shafts, terminals for flues F23L17/02) - F25B: REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A system includes a motor-driven component, a motor configured to operate the motor-driven component, and a motor drive circuit configured to power the motor. The motor drive circuit includes at least one complementary stage, where each stage includes a first transistor and a second transistor. During operation of the motor drive circuit, the first transistor is switched on when the second transistor is switched off. The system includes a controller communicatively coupled to the motor drive circuit. A load condition associated with the component is monitored. Based on the load condition, the controller determines whether the component is operating at a light load condition. If the component is operating at the light load condition, a switching frequency of each of stages is changed from a first switching frequency to a second switching frequency, which is less than the first switching frequency. ## Claims ### Claim 1 A system comprising: a motor-driven component of an HVAC system; a motor configured to operate the motor-driven component; a motor drive circuit configured to power the motor, the motor drive circuit comprising at least one complementary stage, wherein each complementary stage of the at least one complementary stage comprises a first transistor and a second transistor, wherein, during operation of the motor drive circuit, the first transistor is switched on when the second transistor is switched off; and a controller communicatively coupled to the motor drive circuit, the controller operable to: change a switching frequency of each of the one or more complementary stages from a first switching frequency to a second switching frequency, wherein the first switching frequency is about 16 kHz and the second switching frequency is in a range from about 6 kHz to less than 16 kHz, wherein the switching frequency is associated with the rate at which the first and second transistors of each complementary stage are switched between an on and off state; and in response to changing the switching frequency of each of the one or more complementary stages, reduce the number of transition periods by increasing a period of time between being switched from the on and off states for each of the first transistors and the second transistors. ### Claim 2 (depends on 1) The system of claim 1, wherein: the motor drive circuit comprises three complementary stages; and the controller is further configured to change the switching frequency of each complementary stage to the second frequency. ### Claim 3 (depends on 1) The system of claim 1, wherein the controller is further configured to monitor a load condition associated with the motor-driven component and change the switching frequency responsive to the load condition, and the load condition is associated with one or both of a torque associated with the motor-driven component and a motor speed associated with the motor-driven component. ### Claim 4 (depends on 3) The system of claim 3, wherein the controller is further configured to monitor a load condition associated with the motor-driven component and change the switching frequency responsive to the load condition, and the load condition corresponds to one or both of a torque value in a range from about 5 to 20 oz-ft and a motor speed value in a range from about 300 to 500 rotations per minute. ### Claim 5 (depends on 1) The system of claim 1, wherein the controller is further configured to determine the second switching frequency based on calibration information in a lookup table, wherein the lookup table comprises a calibrated switching frequency value for each of a plurality of load conditions for the motor-driven component. ### Claim 6 (depends on 1) The system of claim 1, wherein the motor-driven component is a fan, compressor, or blower of the HVAC system. ### Claim 7 (depends on 6) The system of claim 6, wherein the controller is further configured to: monitor a load condition associated with the motor-driven component and change the switching frequency responsive to the load condition, and the load condition is associated with a cooling demand of the HVAC system; determine a temperature difference between a temperature setpoint associated with the HVAC system and a temperature of space conditioned by the HVAC system; determine that the load condition is a light load condition if the temperature difference is less than a threshold value. ### Claim 8 A method comprising: changing a switching frequency of each of one or more complementary stages of a motor drive circuit configured to operate the motor-driven component from a first switching frequency to a second switching frequency, wherein the first switching frequency is about 16 kHz and the second switching frequency is in a range from about 6 kHz to less than 16 kHz, wherein: the switching frequency is associated with the rate at which a first transistor and a second transistor of each complementary stage are switched between an on and off state; and during operation of the motor drive circuit, for each complementary stage, the first transistor of stage is switched on when the second transistor is switched off; and in response to changing the switching frequency of each of the one or more complementary stages, reducing the number of transition periods by increasing a period of time between being switched from the on and off states for each of the first transistors and the second transistors. ### Claim 9 (depends on 8) The method of claim 8, wherein: the motor drive circuit comprises three complementary stages; and the method further comprises changing the switching frequency of each stage to the second frequency. ### Claim 10 (depends on 8) The method of claim 8, further comprising monitoring a load condition associated with the motor-driven component and changing the switching frequency responsive to the load condition, wherein the load condition is associated with one or both of a torque associated with the motor-driven component and a motor speed associated with the motor-driven component. ### Claim 11 (depends on 10) The method of claim 10, further comprising monitoring a load condition associated with the motor-driven component and changing the switching frequency responsive to the load condition, wherein the load condition corresponds to one or both of a torque value in a range from about 5 to 20 oz-ft and a motor speed value in a range from about 300 to 500 rotations per minute. ### Claim 12 (depends on 8) The method of claim 8, further comprising determining the second switching frequency based on calibration information in a lookup table, wherein the lookup table comprises a calibrated switching frequency value for each of a plurality of load conditions for the motor-driven component. ### Claim 13 (depends on 8) The method of claim 8, wherein the motor-driven component is a fan, compressor, or blower of the HVAC system. ### Claim 14 (depends on 13) The method of claim 13, further comprising: monitoring a load condition associated with the motor-driven component; changing the switching frequency responsive to the load condition, wherein the load condition is associated with a cooling demand of the HVAC system; determining a temperature difference between a temperature setpoint associated with the HVAC system and a temperature of space conditioned by the HVAC system; and determining that the load condition is a light load condition if the temperature difference is less than a threshold value. ### Claim 15 A controller communicatively coupled to a motor-drive circuit associated with a motor-driven component, the controller configured to: cause the motor-drive circuit to transmit a light-load signal to a motor of the motor-driven component; wherein the motor drive circuit comprises at least one complementary stage, each complementary stage of the at least one complementary stage comprising a first transistor and second transistor, wherein, during operation of the motor drive circuit, the first transistor is switched on when the second transistor is switched off; and wherein the motor-drive circuit is configured to change a switching frequency of each of the one or more complementary stages from a first switching frequency to a second switching frequency, wherein the first switching frequency is about 16 kHz and the second switching frequency is in a range from about 6 kHz to less than 16 kHz, wherein the switching frequency is associated with the rate at which the first and second transistors of each complementary stage are switched between an on and off state; and in response to changing the switching frequency of each of the one or more complementary stages, reduce the number of transition periods by increasing a period of time between being switched from the on and off states for each of the first transistors and the second transistors. ### Claim 16 (depends on 15) The controller of claim 15, further configured to monitor a load condition associated with the motor-driven component and change the switching frequency responsive to the load condition, wherein the load condition is associated with one or both of a torque associated with the motor-driven component and a motor speed associated with the motor-driven component. ### Claim 17 (depends on 16) The controller of claim 16, further configured to monitor a load condition associated with the motor-driven component and change the switching frequency responsive to the load condition, wherein the light load condition corresponds to one or both of a torque value in a range from about 5 to 20 oz-ft and a motor speed value in a range from about 300 to 500 rotations per minute. ### Claim 18 (depends on 15) The controller of claim 15, wherein the controller is further configured to determine the second switching frequency based on calibration information in a lookup table, wherein the lookup table comprises a calibrated switching frequency value for each of a plurality of load conditions for the motor-driven component. ### Claim 19 (depends on 15) The controller of claim 15, wherein the motor-driven component is a fan, compressor, or blower of the HVAC system. ### Claim 20 (depends on 15) The controller of claim 15, further configured to: monitor a load condition associated with the motor-driven component; change the switching frequency responsive to the load condition, wherein the load condition is associated with a cooling demand of the HVAC system, wherein the load condition is associated with a cooling demand of the HVAC system; determine a temperature difference between a temperature setpoint associated with the HVAC system and a temperature of space conditioned by the HVAC system; determine that the load condition is a light load condition, if the temperature difference is less than a threshold value.