Method of controlling a brushless permanent-magnet motor
AssigneeDyson Technology Limited
InventorsTuncay CELIK, Libo ZHENG
Life of this patent
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Abstract
A method of controlling a brushless permanent-magnet motor. The method includes dividing each half of an electrical cycle of the motor into a conduction period followed by a primary freewheel period. The conduction period is then divided into a first excitation period, a secondary freewheel period, and a second excitation period. The method then involves exciting a winding of the motor during each excitation period and freewheeling the winding during each freewheel period. The secondary freewheel period has a position and length within the conduction period that acts to reduce the harmonic content of current in the winding relative to back EMF in the winding. As a result, the efficiency of the motor is improved.
Claims18
A method of controlling a brushless permanent-magnet motor, the method comprising:
- dividing each half of an electrical cycle of the motor into a conduction period followed by a primary freewheel period;
- dividing the conduction period into a first excitation period, a secondary freewheel period, and a second excitation period;
- exciting a winding of the motor during each excitation period;
- and freewheeling the winding during each freewheel period, wherein the secondary freewheel period has a position and length within the conduction period that reduces the harmonic content of current in the winding relative to back EMF in the winding.
A method of controlling a brushless permanent-magnet motor, the method comprising operating in dual-switch mode over a first speed range and operating in single-switch mode over a second speed range, wherein the second speed range is higher than the first speed range, each mode comprises dividing each half of an electrical cycle of the motor into a conduction period followed by a primary freewheel period, the single-switch mode comprises exciting a winding of the motor during the conduction period and freewheeling the winding during the freewheel period, and dual-switch mode comprises:
- dividing the conduction period into a first excitation period, a secondary freewheel period and a second excitation period;
- exciting the winding during each excitation period;
- and freewheeling the winding during each freewheel period.
A method of controlling a brushless permanent-magnet motor, the method comprising operating in multi-switch mode over a first speed range and operating in dual-switch mode over a second speed range, wherein the second speed range is higher than the first speed range, multi-switch mode comprises sequentially exciting and freewheeling a winding of the motor multiple times during each half of an electrical cycle of the motor, the winding being freewheeled when current in the winding exceeds a predefined limit, and dual-switch mode comprises:
- dividing each half of an electrical cycle of the motor into a conduction period followed by a primary freewheel period;
- dividing the conduction period into a first excitation period, a secondary freewheel period and a second excitation period;
- exciting the winding during each excitation period;
- and freewheeling the winding during each freewheel period.
A control circuit for a brushless permanent-magnet motor, the control circuit being configured to:
- divide each half of an electrical cycle of the motor into a conduction period followed by a primary freewheel period;
- divide the conduction period into a first excitation period, a secondary freewheel period, and a second excitation period;
- excite a winding of the motor during each excitation period;
- and freewheel the winding during each freewheel period, wherein the secondary freewheel period has a position and length within the conduction period that reduces the harmonic content of current in the winding relative to back EMF in the winding.
A control circuit for a brushless permanent-magnet motor, the control circuit being configured to operate in dual-switch mode over a first speed range and operate in single-switch mode over a second speed range, the second speed range being higher than the first speed range, wherein when operating in each mode the control circuit divides each half of an electrical cycle of the motor into a conduction period followed by a primary freewheel period, when operating in single-switch mode the control circuit excites a winding of the motor during the conduction period and freewheels the winding during the freewheel period, and when operating in dual-switch mode the control circuit:
- divides the conduction period into a first excitation period, a secondary freewheel period and a second excitation period;
- excites the winding during each excitation period;
- and freewheels the winding during each freewheel period.
A control circuit for a brushless permanent-magnet motor, the control circuit being configured to operate in multi-switch mode over a first speed range and operate in dual-switch mode over a second speed range, the second speed range being higher than the first speed range, wherein when operating in multi-switch mode the control circuit sequentially excites and freewheels a winding of the motor multiple times during each half of an electrical cycle of the motor, the winding being freewheeled when current in the winding exceeds a predefined limit, and when operating in dual-switch mode the control circuit:
- divides each half of an electrical cycle of the motor into a conduction period followed by a primary freewheel period;
- divides the conduction period into a first excitation period, a secondary freewheel period and a second excitation period;
- excites the winding during each excitation period;
- and freewheels the winding during each freewheel period.
Dependencies are inferred from the claim text.