A signal generator generates a control signal that causes an inverter to supply a drive current in an AC voltage waveform to each phase of a motor. The signal generator alternately repeats a first energization cycle in which only a switch on an upper side of an arm is set to an ON state and a second energization cycle in which only a switch on a lower side of the arm is set to the ON state in the AC voltage waveform having a third energization cycle therebetween, changes the switches on the upper side and the lower side of the arm to the ON state and an OFF state in order in the third energization cycle, continuously changes an output voltage of the switch that has been further changed to the ON state, and generates a control signal to cause waveforms of the preceding and succeeding first energization cycle and second energization cycle to be continuous with the third energization cycle by varying a phase of the first to the third energization cycles in each phase.

A signal generator generates a control signal that causes an inverter to supply a drive current in an AC voltage waveform to each phase of a motor. The signal generator alternately repeats a first energization cycle in which only a switch on an upper side of an arm is set to an ON state and a second energization cycle in which only a switch on a lower side of the arm is set to the ON state in the AC voltage waveform having a third energization cycle therebetween, changes the switches on the upper side and the lower side of the arm to the ON state and an OFF state in order in the third energization cycle, continuously changes an output voltage of the switch that has been further changed to the ON state, and generates a control signal to cause waveforms of the preceding and succeeding first energization cycle and second energization cycle to be continuous with the third energization cycle by varying a phase of the first to the third energization cycles in each phase.

A method for driving an electric motor includes providing two controllers for driving the electric motor. The two controllers use different control methods to drive the electric motor. The method further includes selecting a first controller of the controllers as a primary controller to drive the electric motor and a second controller of the controllers as a secondary controller, monitoring a control of the electric motor, and switching the control of the electric motor from the primary controller to the secondary controller if an error condition is detected in the control of the electric motor.

A BLDC motor comprising a permanent magnet motor rotor defining a motor axis, a motor housing and a plurality of phase winding circuits mounted on the motor housing to form a stator, wherein each phase winding circuit comprises a phase winding and a driving bridge which is to operate to drive a phase current to flow through the phase winding, and the driving bridge comprises a switching circuit to provide a switched power supply to energize the phase winding; and wherein the phase windings are disposed at different angular positions with respect to the motor axis or the motor housing.

A motor device 100 includes an SPM motor 1 that includes a stator 2 including an iron core 21 and a plurality of windings 23 wound on the iron core 21, and a rotor 3 which is rotatable with respect to a rotation axis and in which a plurality of permanent magnets 33 are mounted along a circumferential direction to form a plurality of magnetic poles in the circumferential direction; and a power supply unit 5 that supplies a current to the plurality of windings 23 of the SPM motor 1. Each of the plurality of magnetic poles is oriented such that directions of axes of easy magnetization are concentrated toward a stator side, and the current supplied from the power supply unit is a trapezoidal wave.

A power tool is provided including a brushless motor having a stator defining a plurality of phases and a rotor. A power unit is provided including power switches operable to deliver power to the motor. A primary controller is interfaced with the power unit to output drive signals to drive the phases of the motor over a series of sectors of the rotor rotation. The primary controller measures a back-electromotive force voltage of the motor and transitions motor commutation from the present sector to the next sector based in relation to the back-EMF voltage. A second controller is provided to receive at least one of the drive signals, calculate a speed and/or direction of rotation of the motor from the drive signals, and take corrective action to cut off supply of power to the motor if it detects an overspeed condition or incorrect direction of rotation.

A power tool is provided including a brushless motor having a stator defining a plurality of phases, a rotor rotatable relative to the stator, and power terminals electrically connected to the phases of the motor. A power unit is provided including power switches. A control unit is interfaced with the power unit to output a drive signal to one or more of the motor switches to drive the phases of the motor over a series of sectors of the rotor rotation. The control unit is configured detect incorrect rotation of the rotor by applying a first series of voltage pulses to a present sector and a second series of voltage pulses to a previous sector, measuring motor currents associated with the first and second series of voltage pulses, and comparing corresponding motor current measurements to detect a transition from the present sector to the previous sector.

A power tool is provided including a brushless motor having a stator defining a plurality of phases and a rotor. A power unit is provided including power switches and a control unit outputs a drive signal to the motor switches to drive the phases of the motor using a trapezoidal control scheme over a series of sectors. The control unit sets a conduction band within which each phase is commutated to a baseline value that is greater than 120 degrees, sets at least one commutation transition point as a function of the set conduction band, and within each sector, monitors an open-phase voltage of the motor to detect a back electromotive force (back-EMF) voltage of the motor and control commutation of at least one phase based on the open-phase voltage of the motor in relation to the at least one commutation transition point.

A power converter includes a plurality of switching elements, a converter circuit that rectifies an AC voltage of an AC power source, a DC link that receives output of the converter circuit and generates a DC voltage, an inverter circuit that converts the DC voltage into an AC voltage of a predetermined frequency through a switching operation, and a control unit that controls the switching operation. A capacitance value of a capacitor is set so that a maximum value of the DC voltage becomes twice or more of a minimum value. The control unit controls the switching elements such that two or more extrema appear in a power source half cycle in a waveform synthesized from second, fourth, and sixth harmonics that have a power source frequency as a fundamental frequency and are extracted from a waveform of an absolute value of a motor current vector.

A motor controller comprises a switch circuit and a driving circuit. The switch circuit is coupled to a motor for driving the motor. The driving circuit generates a plurality of control signals to control the switch circuit. The motor controller is configured to crop a first waveform into a second waveform, where the first waveform is transformed into the second waveform gradually. Moreover, the motor controller is configured to transform the second waveform into the first waveform, where the second waveform is transformed into the first waveform gradually. The first waveform may be an M-shaped waveform, a W-shaped waveform, or a sinusoidal waveform. The second waveform may be a trapezoidal waveform.