An electric power tool includes: a brushless motor having a plurality of stator windings and configured to rotate in accordance with voltages applied to the plurality of stator windings, an induced voltage being generated in accordance with a rotation of the brushless motor; a rectifier circuit configured to rectify an AC voltage; a smoothing capacitor configured to smooth the AC voltage rectified by the rectifier circuit to a pulsation voltage having a maximum value larger than the induced voltage and a minimum value smaller than the induced voltage; and an inverter circuit configured to perform switching operations to output the pulsation voltage to the plurality of stator windings by rotation.

An electric power tool includes: a brushless motor having a plurality of stator windings and configured to rotate in accordance with voltages applied to the plurality of stator windings, an induced voltage being generated in accordance with a rotation of the brushless motor; a rectifier circuit configured to rectify an AC voltage; a smoothing capacitor configured to smooth the AC voltage rectified by the rectifier circuit to a pulsation voltage having a maximum value larger than the induced voltage and a minimum value smaller than the induced voltage; and an inverter circuit configured to perform switching operations to output the pulsation voltage to the plurality of stator windings by rotation.

A power tool comprising a housing and a brushless direct-current (BLDC) motor disposed within the housing. The motor includes a stator and a rotor rotatable relative to the stator. The power tool is configured to generate a power output from the motor such that a quotient obtained by the power output measured in Watts (Wout), divided by an input measured in Volt-Amperes (Vain), and further divided by a diameter of the motor measured in meters (m), is greater than 10 Wout/Vain/m.

A power tool comprising a housing and a brushless direct-current (BLDC) motor disposed within the housing. The motor includes a stator and a rotor rotatable relative to the stator. The power tool is configured to generate a power output from the motor such that a quotient obtained by the power output measured in Watts (Wout), divided by an input measured in Volt-Amperes (Vain), and further divided by a diameter of the motor measured in meters (m), is greater than 10 Wout/Vain/m.

A motor control apparatus includes: an excitation unit configured to excite a plurality of excitation phases of each of a plurality of motors that include first to Nth motors and a control unit configured to control the excitation unit so as to perform detection excitation processing for sequentially exciting the plurality of excitation phases for each excitation cycle during each excitation period, regarding each of the first to Nth motors, and thereby detect rotor positions of the respective first to Nth motors. When detecting rotor positions of the respective first to Nth motors, the control unit delays a start timing of the detection excitation processing of at least one motor out of the first to Nth motors relative to a start timing of the detection excitation processing of another motor by a period shorter than the excitation period.

An electric motor control device that can accurately calculate the rotating speed of an electric motor. The electric motor control device includes a speed calculating unit configured to receive, from a position detector that detects a rotational position of an electric motor and outputs a position detection signal including a periodic error determined according to the rotational position, an input of the position detection signal, receive, from a time detector that outputs a position change time signal obtained by detecting a time period in which the position detection signal output from the position detector changes, an input of the position change time signal, and calculate rotating speed of the electric motor based on the position detection signal and the position change time signal. Further, there is a speed correcting unit for correcting a periodic speed error determined according to the rotational position of the electric motor.

An electric motor control device that can accurately calculate the rotating speed of an electric motor. The electric motor control device includes a speed calculating unit configured to receive, from a position detector that detects a rotational position of an electric motor and outputs a position detection signal including a periodic error determined according to the rotational position, an input of the position detection signal, receive, from a time detector that outputs a position change time signal obtained by detecting a time period in which the position detection signal output from the position detector changes, an input of the position change time signal, and calculate rotating speed of the electric motor based on the position detection signal and the position change time signal. Further, there is a speed correcting unit for correcting a periodic speed error determined according to the rotational position of the electric motor.

A control circuit of a motor control device estimates an initial magnetic pole position of a rotor using an inductive sensing scheme. When estimating the initial magnetic pole position, a drive circuit applies a voltage to a stator winding at each of L electrical angles (L≥5) while changing the L electrical angles. An absolute value of an electrical angle difference of the voltage applied to the stator winding between an i-th time (2≤i≤L) and an i−1st time is 180−360/L degrees or more and 180+360/L degrees or less. An absolute value of an electrical angle difference of the voltage applied to the stator winding between a 1st time for initial position estimation and a last time before starting initial position estimation is 180−360/L degrees or more and 180+360/L degrees or less.

A control circuit of a motor control device estimates an initial magnetic pole position of a rotor using an inductive sensing scheme. When estimating the initial magnetic pole position, a drive circuit applies a voltage to a stator winding at each of L electrical angles (L≥5) while changing the L electrical angles. An absolute value of an electrical angle difference of the voltage applied to the stator winding between an i-th time (2≤i≤L) and an i−1st time is 180−360/L degrees or more and 180+360/L degrees or less. An absolute value of an electrical angle difference of the voltage applied to the stator winding between a 1st time for initial position estimation and a last time before starting initial position estimation is 180−360/L degrees or more and 180+360/L degrees or less.

A motor control apparatus that is configured to perform a power distribution control on three-phase coils of a brushless motor and that is configured to perform a rotation control of a rotor includes: a plurality of switching elements that are arranged to be capable of switching a current which is allowed to flow through the coils; a plurality of sensors that are configured to detect a rotation position of the rotor; and a control part that is configured to output a drive signal for controlling a power distribution pattern of each switching element according to a position detection signal which is obtained by correcting a position detection signal as an output of the plurality of sensors by using a predetermined correction coefficient, wherein the control part is configured to add a correction angle that corresponds to a difference between the position detection signals before and after correction of a predetermined sensor among the plurality of sensors to a setting value of an advance angle of the power distribution control and select an output pattern that includes a plurality of power distribution patterns and that is used when selecting the power distribution pattern, from a plurality of different output patterns in accordance with the advance angle to which the correction angle is added and a power distribution angle of the power distribution control.