Brushless motor having six-step commutation control

Abstract

A power tool is provided including: an electric brushless direct current (BLDC) motor having a rotor and a stator. The stator includes at least six teeth including a first set of teeth on which a first set of stator windings are wound and a second set of teeth on which a second set of stator windings are wound. The first and second sets of stator windings are alternatingly arranged relative to the stator. The first set of stator windings is connected in a wye configuration and the second set of stator windings is connected in delta configuration.

1 . A power tool comprising:
 an electric brushless direct current (BLDC) motor having a rotor and a stator, the stator including at least six teeth including a first set of teeth on which a first set of stator windings are wound and a second set of teeth on which a second set of stator windings are wound;   a power unit electrically connected between a power source and the motor and configured to output at least six voltage signals to the motor; and   a controller configured to control a switching operation of the power unit via at least six drive signals to regulate a supply of power from the power source to the motor,   wherein first and second sets of stator windings are alternatingly arranged relative to the stator, and wherein the first set of stator windings is connected in a wye configuration and the second set of stator windings is connected in delta configuration.   
     
     
         2 . The power tool of  claim 1 , wherein the power unit includes a first switch circuit connected electrically to the first set of stator windings and a second switch circuit connected electrically to the second set of windings of the plurality of windings. 
     
     
         3 . The power tool of  claim 2 , wherein the controller is configured to drive the first switch circuit and the second switch circuit using a six-phase commutation sequence. 
     
     
         4 . The power tool of  claim 2 , wherein drive signals for the first switch signal are advanced by a lead angle compared to drive signals for the second switch circuit. 
     
     
         5 . The power tool of  claim 4 , wherein the lead angle is approximately 30 degrees. 
     
     
         6 . The power tool of  claim 4 , wherein a first phase current corresponding to the first set of stator windings and a second phase current corresponding to the second set of stator windings are in line with a back-electromagnetic force (back-EMF) voltage of the motor. 
     
     
         7 . The power tool of  claim 4 , wherein a first motor line current corresponding to the first set of stator windings is shifted by approximately the lead angle compared to a second motor line current corresponding to the second set of stator windings. 
     
     
         8 . The power tool of  claim 1 , wherein the power supply comprises an alternating-current (AC) power supply. 
     
     
         9 . The power tool of  claim 8 , further comprising a bridge rectifier arranged to generate a positive voltage waveform from the AC power supply. 
     
     
         10 . The power tool of  claim 9 , further comprising a capacitor coupled to an output of the bridge rectifier. 
     
     
         11 . The power tool of  claim 1 , wherein the first switch circuit and the second switch circuit both comprise a plurality of insulated-gate bipolar transistors (IGBTs). 
     
     
         12 . The power tool of  claim 1 , wherein the first switch circuit and the second switch circuit both comprise a plurality of field-effect transistors (FETs). 
     
     
         13 . A system including a brushless direct current (BLDC) motor comprising:
 a rotor;   a stator including at least six teeth including a first set of teeth on which a first set of stator windings are wound and a second set of teeth on which a second set of stator windings are wound; and   at least six input terminals arranged to receive at least six voltage signals of which three voltage signals are arranged to energize the first set of stator windings and three voltage signals are arranged to energize the second set of stator windings independently of the first set of stator windings;   wherein first and second sets of stator windings are alternatingly arranged relative to the stator, and wherein the first set of stator windings is connected in a wye configuration and the second set of stator windings is connected in delta configuration.   
     
     
         14 . The system of  claim 13 , further comprising:
 a power unit electrically connected between a power source and the motor and configured to output at least six voltage signals to the motor; and   a controller configured to control a switching operation of the power unit via at least six drive signals to regulate a supply of power from the power source to the motor.   
     
     
         15 . The system of  claim 14 , wherein the power unit includes a first switch circuit connected electrically to the first set of stator windings and a second switch circuit connected electrically to the second set of windings of the plurality of windings. 
     
     
         16 . The system of  claim 15 , wherein the controller is configured to drive the first switch circuit and the second switch circuit using a six-phase commutation sequence. 
     
     
         17 . The system of  claim 15 , wherein drive signals for the first switch signal are advanced by a lead angle compared to drive signals for the second switch circuit. 
     
     
         18 . The system of  claim 17 , wherein the lead angle is approximately 30 degrees. 
     
     
         19 . The system of  claim 17 , wherein a first phase current corresponding to the first set of stator windings and a second phase current corresponding to the second set of stator windings are in line with a back-electromagnetic force (back-EMF) voltage of the motor. 
     
     
         20 . The system of  claim 17 , wherein a first motor line current corresponding to the first set of stator windings is shifted by approximately the lead angle compared to a second motor line current corresponding to the second set of stator windings.