Abstract: A method and apparatus for braking a motor has a braking power switching device coupled across windings of the motor. To brake the motor, the braking power switching device is cycled on and off.

Abstract: A method and apparatus for braking a motor has a braking power switching device coupled across windings of the motor. To brake the motor, the braking power switching device is cycled on and off.

Abstract: A system and method for reducing the cost of producing a brushless DC motor is presented. The brushless DC motor provides higher power density and efficiency with an increased tool run time. The brushless DC motor includes a rotor assembly that has an unmagnetized permanent magnet affixed to a shaft. The permanent magnet remains unmagnetized until the motor is partially assembled. A plurality of coils for producing a magnetic field are wound about the rotor assembly. The coils include end turns that enclose the rotor assembly such that the rotor assembly is not removable. Since the windings are wound with the rotor assembly already enclosed, the windings do not require large end coils to allow subsequent insertion of the rotor. Minimizing the end coils reduces the length of wire required per turn, thereby reducing the resistance of the winding.

Abstract: A system and method for controlling a brushless DC motor (58) is provided. The motor (58) includes a rotor (72) and a stator (96) having at least three phases. The rotor (72) is magnetically coupled to and moveable by the stator (96) when the coils (94) are appropriately energized. Each of the coils (94) is characterized by a corresponding voltage waveform. No more than two position sensors (122) are provided for sensing the position of the rotor (72) during a start-up mode. Each position sensor (122) has an associated position sensor signal. The position sensors (122) are aligned to sense the rotor position such that each position sensor signal indicates a zero torque point corresponding to a phase voltage waveform. The position of the rotor (72) is sensed such that the position sensor signals indicate the start-up operating state of the motor (58). During a first ambiguous start-up state, two predetermined coils (94) are alternately energized.

Abstract: An excitation circuit for a flux switching motor. The circuit includes a low-value film capacitor across the DC side of a bridge rectifier. A plurality of electronic switches are arranged in an H-bridge configuration for switching current flow through an armature winding of the motor in accordance with a PWM control scheme and single-pulse control scheme controlled by a microcontroller. A start-up diode is placed across the field winding of the motor and is electronically switched out of the circuit after a startup phase of the motor has completed. The circuit implements armature energy recirculation through the field winding during startup to promote more uniform and quicker startup of the motor. The use of a film capacitor improves the power factor of the circuit, helps to eliminate the introduction of harmonics into the AC voltage source, and helps in mitigating EMI. Reverse commutation is used to bring the motor to a quick stop when it is powered off.

Abstract: A system and method for controlling a brushless DC motor (58) is provided. The motor (58) includes a rotor (72) and a stator (96) having at least three phases. The rotor (72) is magnetically coupled to and moveable by the stator (96) when the coils (94) are appropriately energized. Each of the coils (94) is characterized by a corresponding voltage waveform. No more than two position sensors (122) are provided for sensing the position of the rotor (72) during a start-up mode. Each position sensor (122) has an associated position sensor signal. The position sensors (122) are aligned to sense the rotor position such that each position sensor signal indicates a zero torque point corresponding to a phase voltage waveform. The position of the rotor (72) is sensed such that the position sensor signals indicate the start-up operating state of the motor (58). During a first ambiguous start-up state, two predetermined coils (94) are alternately energized.

Abstract: A system and method for reducing the cost of producing a brushless DC motor (58) is presented. The brushless DC motor (58) provides higher power density and efficiency with an increased tool run time. The brushless DC motor (58) includes a rotor assembly (72) that has an unmagnetized permanent magnet (74) affixed to a shaft. The permanent magnet (74) remains unmagnetized until the motor is partially assembled. A plurality of coils (94) for producing a magnetic field are wound about the rotor assembly (72). The coils (94) include end turns that enclose the rotor assembly (72) such that the rotor assembly (72) is not removable. Since the windings (94) are wound with the rotor assembly (72) already enclosed, the windings (94) do not require large end coils to allow subsequent insertion of the rotor (72). Minimizing the end coils reduces the length of wire required per turn, thereby reducing the resistance of the winding (94).