A power tool is provided including a brushless DC (BLDC) motor, a rectifier that receives an alternative current from a power supply and outputs a rectified signal supplied to a DC power bus, and an inverter circuit having motor switches connected electrically between the DC power bus and the motor. A control module controls a switching operation of the power switches to regulate supply power from the power supply to the motor. The control module controls the switching operation so as to, within a half cycle of the AC power supply voltage waveform, increase current draw from the power supply from a first threshold at or after a first zero-crossing of the half cycle up to a second threshold, and reduce current draw from the power supply from the second threshold up to a third threshold at or prior to a second zero-crossing of the half cycle.

A power tool is provided including a brushless DC (BLDC) motor, a rectifier that receives an alternative current from a power supply and outputs a rectified signal supplied to a DC power bus, and an inverter circuit having motor switches connected electrically between the DC power bus and the motor. A control module controls a switching operation of the power switches to regulate supply power from the power supply to the motor. The control module controls the switching operation so as to, within a half cycle of the AC power supply voltage waveform, increase current draw from the power supply from a first threshold at or after a first zero-crossing of the half cycle up to a second threshold, and reduce current draw from the power supply from the second threshold up to a third threshold at or prior to a second zero-crossing of the half cycle.

The present invention relates to an electromagnetic machine comprising: rotation shaft; a stator comprising a multi-phase winding wire; a mover (rotor 1) comprising the multi-phase winding wire and spaced apart from the stator at a preset interval; and a controller for independently controlling a first magnetic field of the stator and a second magnetic field of the mover (rotor 1). The electromagnetic machine according to the present invention can resolve, by means of the mover (rotor 1) and the wound-type stator that can be independently and actively controlled, a torque issue at start-up or when needed and, thereby, has the effects of producing a maximum driving torque while having a minimum size, and of maximizing efficiency.

An electric machine includes a stator and a rotor energizable by magnetic fields produced by the stator when receiving a stator current to produce relative motion between the rotor and the stator. A controller is configured to send the stator current through the stator at a current angle measured from the closest one of a pole of the rotor, determine a desired operational output of the electric machine, and determine a desired rotor motion corresponding to the desired operational output of the electric machine. The controller is further configured to calculate a vector control modulation applied to the stator that elicits the desired rotor motion, and adjust the current angle of the stator current based on the vector control modulation to cause the rotor to perform the desired rotor motion and achieve the desired operational output of the electric machine.

A resonant power supply, a primary-side feedback excitation power supply controller, a method, and a control apparatus are disclosed. In the resonant power supply, a bridge circuit is electrically connected to a power supply. The bridge circuit is configured to convert, based on a drive signal, a direct current provided by the power supply into a square wave signal. An LC series resonant network is electrically connected to the bridge circuit and a primary-side winding. The LC series resonant network is configured to convert the square wave signal into an alternating current, and output the alternating current to the primary-side winding. The alternating current includes an input voltage Vt and an input current I.sub.r.

A resonant power supply, a primary-side feedback excitation power supply controller, a method, and a control apparatus are disclosed. In the resonant power supply, a bridge circuit is electrically connected to a power supply. The bridge circuit is configured to convert, based on a drive signal, a direct current provided by the power supply into a square wave signal. An LC series resonant network is electrically connected to the bridge circuit and a primary-side winding. The LC series resonant network is configured to convert the square wave signal into an alternating current, and output the alternating current to the primary-side winding. The alternating current includes an input voltage Vt and an input current I.sub.r.

A control system for a multiphase electric motor comprises processing means arranged to determine a pattern of PWM voltage waveforms to be applied to respective phases of the motor, the processing means assigning different PWM patterns for use with different motor positions. In use for a given rotational position of the motor the processing means is normally adapted to apply PWM waveforms according to the assigned PWM pattern unless a different PWM pattern is currently in use at that time, except that in the event that the demanded voltage waveforms cannot be achieved with the current PWM pattern the processing means is adapted to force the PWM pattern to change. Upon the rotor moving into a different position associated with a different assigned pattern the processing means forces the PWM pattern to change to the assigned PWM pattern.

A control system for a multiphase electric motor comprises processing means arranged to determine a pattern of PWM voltage waveforms to be applied to respective phases of the motor, the processing means assigning different PWM patterns for use with different motor positions. In use for a given rotational position of the motor the processing means is normally adapted to apply PWM waveforms according to the assigned PWM pattern unless a different PWM pattern is currently in use at that time, except that in the event that the demanded voltage waveforms cannot be achieved with the current PWM pattern the processing means is adapted to force the PWM pattern to change. Upon the rotor moving into a different position associated with a different assigned pattern the processing means forces the PWM pattern to change to the assigned PWM pattern.

A motor is provided with stator windings arranged on a circumference of stator. Multiple-phase currents are supplied to the stator windings. A current is supplied to rotor windings. The multiple-phase currents include torque current components, which are arranged to be opposite in directions to torque current components of the current. By this mutually opposite-directional current arrangement, a sum of both torque current components results in a magnetomotive force of zero. It is also possible to reduce influence of the torque current components on the field magnetic fluxes of the motor. In the motor, circumferential magnetic flux components can be concentrated on an airgap and a portion near therearound, so that a larger amount of torque can be obtained, and constant output control can be performed more easily.

An AC electric motor drive system includes a power supply transformer connected to an AC power supply and insulating an AC power supply side and a load side; an AC electric motor; a power converter which converts AC voltage outputted from the power supply transformer to output AC voltage, and which outputs the output AC voltage to the AC electric motor; and a capacitive component having one end connected to the load side of the power supply transformer, and another end grounded.