A method for determining an initial rotor position of a permanent magnet synchronous motor (PMSM) includes: generating a plurality of transient currents by applying a plurality of voltages to each phase stator winding of a three phase stator winding of the PMSM; generating three phase current differences according to the plurality of transient currents; determining a first zone in which the initial rotor position of the PMSM is located according to the three phase current differences, wherein angles between 0-360 degrees are divided into a plurality of zones, and the first zone is selected from the plurality of zones; calculating three line current differences according to the three phase current differences; and determining the initial rotor position of the PMSM according to the first zone and the three line current differences.

A controller of a power tool outputs a driving signal to a motor driving circuit and acquires a position of a rotor of a brushless motor. While acquiring the position of the rotor of the brushless motor, a phase voltage or a line voltage of a winding of the brushless motor is detected through the voltage detection circuit. Whether an upper bridge arm switching element, a lower bridge arm switching element, and/or the brushless motor is short-circuited is determined according to the phase voltage or the line voltage of the winding of the brushless motor.

A method for controlling switched reluctance machine (SRM) utilizing a SRM control system. The method allows for adaptive pulse positioning over a wide range of speeds and loads. An initial rotor position is provided for the SRM utilizing an initialization mechanism. A pinned point on a phase current waveform is defined during an initial current rise phase of the current waveform. A slope of the current rise is determined as the current waveform reaches the pinned point. The slope is then fed to the commutation module of the SRM control system. An error signal from calculated inductance or current slope is used as an input to a control loop in the SRM control system. The time determining module determines an optimum time signal to fire a next pulse. The optimum time signal is fed to the SRM for turning the plurality of SRM switches to on and off states.

Methods and apparatus for determining a position of a rotor in a three-phase motor by determining first and second ones of sectors in which a first one of the magnetic poles of the rotor may be positioned by respectively driving phase pairs complementary signals and examining a voltage of a floating one of the phases. Embodiments can include applying torque to the motor by driving at least one phase pair with respective signals aligned in phase and unequal duty cycles to move the rotor a given amount from the rotor position in the first or second ones of the sectors for determining the position of the rotor.

A drive device of a synchronous motor includes a power converter that drives the synchronous motor by sequentially applying positive and negative voltages to respective phases of the synchronous motor; a current detection unit that detects a phase current; and a magnetic pole position estimation unit estimating a magnetic pole position of a rotor based on the phase current. The magnetic pole position estimation unit acquires maximum and minimum values of the phase current while the synchronous motor is stopped, calculates a first magnetic pole position from a subtracted value of an absolute value of the maximum and minimum values, calculates a second magnetic pole position from an added value of the absolute value of the maximum and minimum values, discriminates a polarity of a magnet of the rotor, and estimates an initial magnetic pole position of the rotor from the polarity and the second magnetic pole position.

A motor drive circuit provides a drive signal to an electronically commutated motor. A control circuit the motor drive circuit based on calibration data. The calibration data indicate a relationship between an actual angular position of a rotor of the motor in response to the drive signal and an expected angular position of a rotor of an ideal motor in response to the drive signal.

A method for detecting an initial position of a rotor of a permanent magnet synchronous motor in a no-load environment can comprise the steps of: estimating a temporary initial position α′ by means of aligning a d axis; measuring a first voltage command which is output by performing velocity control within predetermined velocity ranges with respect to the forward direction of a motor on the basis of the temporary initial position α′; measuring a second voltage command which is output by performing velocity control within the predetermined velocity range with respect to the reverse direction of the motor on the basis of the temporary initial position α′; calculating respective variations of the first voltage command and second voltage command, and calculating a compensation angle α″; and calculating an initial position α of the rotor on the basis of the sum of the temporary initial position α′ and compensation angle α″.

A variable speed drive comprises an output for delivering a drive voltage to an electric motor, power inverter, a drive controller, and a current sensor. The drive controller includes a PWM generator, a control law module, and a state variable estimator for estimating a state variable of the electric motor. The module computes a target voltage signal based on state variable estimates provided by the estimator and outputs the target voltage signal to the PWM generator. The generator approximates the target voltage signal with a PWM control signal, controls the inverter using the control signal, computes, based on the deviation between the control signal and the target voltage signal, an estimation support signal, and outputs the estimation support signal to the estimator. The estimator estimates a state variable of the motor based on the estimation support signal and the drive current, and outputs the estimate to the module.

A method for controlling switched reluctance machine (SRM) utilizing a SRM control system. The method allows for adaptive pulse positioning over a wide range of speeds and loads. An initial rotor position is provided for the SRM utilizing an initialization mechanism. A pinned point on a phase current waveform is defined during an initial current rise phase of the current waveform. A slope of the current rise is determined as the current waveform reaches the pinned point. The slope is then fed to the commutation module of the SRM control system. An error signal from calculated inductance or current slope is used as an input to a control loop in the SRM control system. The time determining module determines an optimum time signal to fire a next pulse. The optimum time signal is fed to the SRM for turning the plurality of SRM switches to on and off states.

A motor control apparatus includes: a switching power supply; a first motor configured to operate with a voltage from the switching power supply; and a control unit configured to control the first motor, wherein the control unit is further configured to cause the switching power supply to supply power of the switching power supply to a load other than the first motor before detecting an initial position of a rotor of the first motor using a current flowing through the first motor.