A chiller system includes a compressor configured to circulate a refrigerant between an evaporator and a condenser in a closed refrigerant loop and a synchronous motor configured to drive the compressor. The motor includes a stator winding and a rotor. The chiller system includes a controller configured to estimate a flux linkage of the rotor and generate a control signal for the motor based on the estimated flux linkage. Estimating the flux linkage includes applying a voltage of the stator winding to a transfer function having an error correction variable, using a first value of the error correction variable in the transfer function to obtain convergence of the flux linkage over an initial motor starting interval, and using a second value of the error correction variable after the initial motor starting interval to reduce an error in estimating the flux linkage.

A sensorless electric motor control device is provided that completes a phase detection of a rotor before an activation signal is received, so as to shorten a time period from when the activation signal is received to when the rotor reaches a target number of rotations. The control device for a sensorless electric motor 10 includes an inverter 11 that drives the electric motor 10 and a first processor 18 that serves as a phase detection unit that causes the inverter 11 to perform a phase detection before the inverter 11 receives an activation signal that activates the electric motor 10, wherein the phase detection aligns a magnetic pole of a rotor of the electric motor 10 with a predetermined position with respect to a stator.

To avoid control failure resulting from startup of a PMSM that is windmilling, initial speed and position are determined before startup. A controller uses a FOC routine having a speed PI control loop, field-weaken control, a current PI control loop, and a speed observer. When the controller receives an instruction to start the PMSM, it delays startup and executes an estimation stage, in which the controller executes the FOC routine but with the speed PI control loop and the field-weaken control disabled. The estimation stage is repeated multiple times, with estimates converging to actual speed and position through successive iterations. When estimated speed and position values have stabilized, the motor is started using the estimates as initial speed and position for driving the PMSM. The FOC routine, with the speed PI control loop and the field-weaken control enabled, is used to drive the PMSM.

Disclosed is a sensorless control system for a permanent magnet synchronous machine. The sensorless control system includes a counter electromotive force estimation unit configured to estimate a counter electromotive force using a phase voltage reference applied to an inverter and a phase current applied from the inverter to the permanent magnet synchronous machine, and a speed estimation unit configured to estimate an angular velocity and an electrical angle of a rotor of the permanent magnet synchronous machine, and the counter electromotive force estimation unit according to one embodiment of the present disclosure may maintain robust performance at a low speed by modifying some portion of a conventional Luenberger observer.

A chiller system includes a compressor configured to circulate a refrigerant between an evaporator and a condenser in a closed refrigerant loop and a synchronous motor configured to drive the compressor. The motor includes a stator winding and a rotor. The chiller system includes a controller configured to estimate a flux linkage of the rotor and generate a control signal for the motor based on the estimated flux linkage. Estimating the flux linkage includes applying a voltage of the stator winding to a transfer function having an error correction variable, using a first value of the error correction variable in the transfer function to obtain convergence of the flux linkage over an initial motor starting interval, and using a second value of the error correction variable after the initial motor starting interval to reduce an error in estimating the flux linkage.

A method for operating an electric motor when at a rotational speed below or above a predetermined limit value. The method involves operating an electric motor that has a stator and a rotor, wherein the stator or the rotor has at least three segments each having at least one electromagnetic element. The method includes simultaneously de-energizing all electromagnetic elements of all segments while the rotor rotates, measuring an electrical quantity induced in the electromagnetic elements, in particular an induced voltage, for each segment, and determining a rotor position of the rotor in relation to the stator from the measured electrical quantities. An electrical current can be supplied to the electromagnetic elements such that a segment magnetic field is formed to provide a segment torque to the rotor. The intensity of the electrical current depends on a segment position of the rotor in relation to the segment.

A chiller system includes a compressor configured to circulate a refrigerant between an evaporator and a condenser in a closed refrigerant loop and a synchronous motor configured to drive the compressor. The motor includes a stator winding and a rotor. The chiller system includes a controller configured to estimate a flux linkage of the rotor and generate a control signal for the motor based on the estimated flux linkage. Estimating the flux linkage includes applying a voltage of the stator winding to a transfer function having an error correction variable, using a first value of the error correction variable in the transfer function to obtain convergence of the flux linkage over an initial motor starting interval, and using a second value of the error correction variable after the initial motor starting interval to reduce an error in estimating the flux linkage.

A method and system for adaptive sensorless determination of the position of a PMSM motor is described. The system and method include: determining the rotor position and the rotor polarity by means of discrete signal injection for the range between standstill up to low rotational speed; determining the rotor position by means of continuous signal injection at a rotational speed that is lower than a first changeover speed; determining the rotor position by means of back EMF at a rotational speed that is higher than the first changeover speed; wherein by means of a motor control system, depending on the rotational speed, a switch is made between rotor position determination by continuous signal injection and rotor position determination by back EMF; and wherein during movement of the rotor, the rotor polarity and/or the rotor position are/is monitored and optionally adjusted at a point in time using the rotor polarity and/or the rotor position at a previous point in time.

A power tool and a motor drive circuit thereof are provided. The motor drive circuit includes an inverter, a controller and a current sensor. The inverter includes a plurality of semiconductor switches and configured to convert a voltage from a power supply into an alternating current for an electric motor. The controller is configured to output detecting signals and drive signals for the inverter. The current sensor is configured to sample a current flowing through the motor, the current comprising a plurality of driving current portions corresponding to the drive signals and a plurality of position detecting current portions corresponding to the detecting signals. The controller determines the drive signals at least based on the position detecting current portions of the current so as to control power modes of the semiconductor switches in the inverter in a starting stage of the motor.

To achieve smooth switching of control without fluctuations in speed and torque, an excitation current command is allowed to transit linearly or in accordance with the function of speed between a value under sensorless vector control and a value under low-speed region control in accordance with a speed command or estimated speed in a speed region where the control is switched or in an adjacent speed region where sensorless vector control is performed. Therefore, abrupt variations in excitation current are reduced before and after the switching of the control.