A motor drive controlling apparatus includes a controller that generates a drive control signal in response to input of a speed command signal and a motor driver that generates a drive signal in response to input of the drive control signal and outputs the drive signal to a motor, and the controller repeatedly generates the drive control signal in a period during which the speed command signal is inputted and stops generating the drive control signal in a period during which the speed command signal is not inputted to repeat an operation period in which the motor performs rotational operation and a stop period in which the motor stops operating in a non-excited state.

A motor control device that detects a motor current through ΔΣ AD conversion includes a stop signal generator and a stop signal controller. When a difference between a maximum value and a minimum value of three phase voltage command values to be applied to a motor is smaller than or equal to a predetermined threshold, a stop signal that causes the ΔΣ AD conversion to stop is output with a delay by the time corresponding to a delay in current detection while a leakage current caused by on and off of a power conversion element is occurring.

A power tool is provided including a housing, a brushless motor disposed within the housing, a power switch circuit that supplies power from a power source to the brushless motor, and a controller configured to receive at least one signal associated with a phase current of the motor, detect an angular position of the rotor based on the phase current of the motor, and apply a drive signal to the power switch circuit to control a commutation of the motor based on the detected angular position of the rotor. If the supply of power to the motor is turned OFF to cause the motor to slow down and is turned back ON while the rotor speed exceeds a speed threshold, the controller electronically brakes the motor for a time interval to measure the phase current of the motor and detects the angular position of the rotor based on the measured phase current.

A driving circuit for a semiconductor circuit which includes a pair of main terminals through which a main current is conducted and a control terminal to which a control voltage is applied to control a circulation state of the main current, includes: driving voltage switching circuitry that receives a control signal, instructs switching between driving voltages based on a change in the control signal, and outputs a driving voltage, among the driving voltages, that has been selected in the switching; low-speed control circuitry that instructs an increase-decrease change in the control voltage at a low speed; speed-increase control circuitry that executes a speed-increase control of increasing a speed of the increase-decrease change made by the low-speed control circuitry; and speed-increase switching circuitry that instructs switching between an execution and a non-execution of the speed-increase control, and instructs switching between levels of a speed-increase change caused by the speed-increase control.

A method for estimating the position of a rotor of a synchronous electrical machine, includes a rotor and a stator coupled to an inverted synchronous electrical machine via a rectifier comprising the following steps: measurement of a current i.sub.abc circulating in the stator of the synchronous electrical machine; determination of two signals in quadrature i.sub.α; i.sub.β according to a stationary reference frame from the current i.sub.abc and isolation of two filtered signals i.sub.αh; i.sub.βh from the two signals in quadrature i.sub.α; i.sub.β; demodulation of the two filtered signals i.sub.αh; i.sub.βh in order to obtain two demodulated signals i.sub.αobs, i.sub.βobs, obtaining of an estimated position {circumflex over (θ)} of the rotor from the two demodulated signals i.sub.αobs, i.sub.βobs.

A motor drive method is a method of driving a motor by a motor drive apparatus. The motor drive apparatus includes an inverter that regulates supply power to the motor that is a synchronous machine and includes a controller that controls the inverter. The method includes changing, before loss of synchronism, a speed of the motor from a second speed range to a first speed range. A speed range in which the motor is operable at a substantially fixed speed is the first speed range, and a speed range that is lower than the first speed range and includes zero speed is the second speed range.

A motor drive method is a method of driving a motor by a motor drive apparatus. The motor drive apparatus includes an inverter that regulates supply power to the motor that is a synchronous machine and includes a controller that controls the inverter. The method includes changing, before loss of synchronism, a speed of the motor from a second speed range to a first speed range. A speed range in which the motor is operable at a substantially fixed speed is the first speed range, and a speed range that is lower than the first speed range and includes zero speed is the second speed range.

A position estimation device acquires detection values of magnetic field strength at three or more locations of a rotor in a range where a rotor angle is less than one rotation. A section is selected based on a detection value of the magnetic field strength from predetermined sections for a pole pair number of the rotor. A feature amount calculator is provided to calculate feature amounts of a waveform of the magnetic field strength based on a combination of the detection values of the magnetic field strength according to the section selected. An estimator is provided to determine, for each segment associated with the section selected, whether or not a magnitude relationship of the feature amounts learned in advance coincides with a magnitude relationship of the feature amounts calculated, and estimating, as a rotation position of the rotor, the pole pair number associated with the segment having the same magnitude relationship.

A motor drive system capable of suppressing heat generation during a low speed operation may include: an inverter including a plurality of switching elements to convert direct current power to alternating current power having a plurality of phases; a motor driven with the alternating current power converted in the inverter; and a controller determines an operating point of the motor on the basis of a torque command of the motor and generates a d-axis current command and a q-axis current command corresponding to the operating point. In particular, when each of the switching elements is overheated, the controller changes the d-axis current command and the q-axis current command by changing the operating point to a different operating point corresponding to a torque of the same magnitude as the torque command.

A motor drive system capable of suppressing heat generation during a low speed operation may include: an inverter including a plurality of switching elements to convert direct current power to alternating current power having a plurality of phases; a motor driven with the alternating current power converted in the inverter; and a controller determines an operating point of the motor on the basis of a torque command of the motor and generates a d-axis current command and a q-axis current command corresponding to the operating point. In particular, when each of the switching elements is overheated, the controller changes the d-axis current command and the q-axis current command by changing the operating point to a different operating point corresponding to a torque of the same magnitude as the torque command.