The inverter (110) comprises input terminals (IT+, IT−), output terminals (OT), controllable switches (Q, Q′) connected to the input terminals (IT+, IT−) and to the output terminals (OT) and a control device (116) configured to control the controllable switches (Q, Q′) so as to convert a DC voltage at the input terminals (IT+, IT−) into an AC voltage at the output terminals (OT) intended to drive an asynchronous electric motor (108) to achieve a target torque (T*), selectively: in a first mode of operation in which the target torque (T*) is determined according to a torque determination method, and in response to a rotor temperature (Tr), in a second mode of operation in which losses in the rotor are decreased relative to the first mode of operation while the target torque (T*) remains determined according to the torque determination method of the first mode of operation.

An iron loss reduction control apparatus for motor permanent magnet overtemperature protection is provided. The apparatus includes: a permanent magnet temperature prediction unit configured to predict a temperature of a permanent magnet in a motor based on a driving state of the motor; a first iron loss reduction unit configured to adjust a switching frequency of a switching element in an inverter providing a driving power to the motor based on the temperature of the permanent magnet; and a second iron loss reduction unit configured to adjust a current command of the motor based on the temperature of the permanent magnet.

An electric motor for viscous pumping, wherein the electric motor is a brushless DC motor configured to be driven by a low DC voltage of around 40-60 VDC, and includes: a rotor with permanent magnets; a stator with a stack of laminations and windings wound therearound; and a controller to provide electronic commutation of electric current flowing through the windings; wherein the windings and the stack of laminations are configured to handle at least 1 kW of continuous electric power from the controller, and the controller includes a feedback circuit including a rotation sensor coupled to the rotor and having an angular resolution of at least 1/500th of a revolution to allow the controller to control the torque generated by the electric motor to a corresponding extent.

An electric motor for viscous pumping, wherein the electric motor is a brushless DC motor configured to be driven by a low DC voltage of around 40-60 VDC, and includes: a rotor with permanent magnets; a stator with a stack of laminations and windings wound therearound; and a controller to provide electronic commutation of electric current flowing through the windings; wherein the windings and the stack of laminations are configured to handle at least 1 kW of continuous electric power from the controller, and the controller includes a feedback circuit including a rotation sensor coupled to the rotor and having an angular resolution of at least 1/500th of a revolution to allow the controller to control the torque generated by the electric motor to a corresponding extent.

A motor controller comprises a switch circuit and a control unit. The switch circuit is coupled to a motor for driving the motor. The control unit generates a control signal to control the switch circuit. The motor controller determines a non-excitation time. When the motor is in a locked state, the motor controller enables the non-excitation time to be a variable value. The motor controller utilizes the non-excitation time to achieve a lock protection function. The motor controller determines whether the motor is in the locked state by detecting a rotor speed or a rotor temperature. Moreover, the motor controller further comprises a driving signal, where the driving signal has the non-excitation time.

A rotating machine control device for controlling a rotating machine having a stator winding and a field winding includes a current command generation unit which generates a current command value on the basis of the temperature of the rotating machine. The current command generation unit includes a constraint condition setting unit which calculates a constraint condition on the basis of a torque command, stator winding voltage, stator winding current, and field winding current, an optimization calculation unit which calculates and outputs the current command value, using the constraint condition and an evaluation function, and a constraint condition update unit which updates the constraint condition on the basis of the temperature of the rotating machine. The current command generation unit calculates and outputs the current command value, using the updated constraint condition.

An electric motor control device includes an inverter circuit, which has a power conversion circuit configured of six switching elements, and a switching control circuit that controls the switching elements in such a way as to be turned on or off, wherein, when it is determined that the inverter circuit is in an abnormal state, an execution of a three-phase short-circuiting process, whereby all upper side switching elements or all lower side switching elements are turned on, or a six-switch opening process, whereby all the switching elements are turned off, is selected based on a temperature of at least one permanent magnet of an electric motor, in accordance with an operating state of the electric motor.

An estimation unit estimates a first coil temperature in a state where the motor is stopped, and a second coil temperature in a state where the motor is driven, and the control unit controls the driving of the motor based on the first coil temperature and the second coil temperature.

An estimation unit estimates a first coil temperature in a state where the motor is stopped, and a second coil temperature in a state where the motor is driven, and the control unit controls the driving of the motor based on the first coil temperature and the second coil temperature.

An iron loss reduction control apparatus for motor permanent magnet overtemperature protection is provided. The apparatus includes: a permanent magnet temperature prediction unit configured to predict a temperature of a permanent magnet in a motor based on a driving state of the motor; a first iron loss reduction unit configured to adjust a switching frequency of a switching element in an inverter providing a driving power to the motor based on the temperature of the permanent magnet; and a second iron loss reduction unit configured to adjust a current command of the motor based on the temperature of the permanent magnet.