Disclosed is an AC motor drive (600) for a three phase, 400 Hz., AC induction motor. The application is a constant speed , constant load application. An AC power source with a wide variation in voltage and frequency is rectified to establish a DC bus. A three phase full wave bridge inverter operates on this source. A cascaded sinusoidal reference signal generator (225) generates three sinusoidal voltages 120° phase shifted from one another. These pure sinusoidal reference help reduce harmonic currents. A high PWM frequency is used to operate the power switches of the bridge to reduce current harmonics. The speed regulator (220) generates an error voltage between a speed command voltage and a feedback of DC voltage that is equivalent to the RMS value of the terminal voltage of the motor for speed regulation. The harmonic content of the DC bus current is extracted to provide short circuit protection.

According to some embodiments, AC chopping circuit includes a switching circuit, a synchronizing signal generating circuit, a switch driving circuit and an auxiliary power supplying circuit. In some examples, the switching circuit are coupled to an AC power source and a load. In certain examples, the synchronizing signal generating circuit provides a synchronizing signal which is related to a polarity of the AC power source. In some examples, the switching circuit is controlled based at least in part on the synchronizing signal.

In an example, a system for determining a power factor of an electric device powered by an alternating current (AC) power is described. The system includes a current sensor configured to: (i) remotely sense, at a position external to the electric device, a magnetic field formed by the AC power in the electric device, and (ii) determine, based on the sensed magnetic field, a current of the AC power. The system also includes a voltage sensor configured to, at a position external to the electric device, remotely measure a voltage of the AC power. The system further includes a computing device communicatively coupled to the current sensor and the voltage sensor, the computing device being configured to: (i) determine a phase delay between the current and the voltage, and (ii) determine, based on the phase delay, a power factor of the electric device.

The present invention provides a device and a method for changing over an electric machine from the regular operating mode into the open-circuit mode. In order to avoid excessive increases in voltage and associated adverse effects on the electric machine and the other components, in particular batteries, a further control phase is introduced between the end of the regular operating mode and the freewheeling mode, during which further control phase the voltage at the terminals of the electric machine is continuously adjusted from the voltage previously set in the regular operating mode to the expected open-circuit voltage of the electric machine.

A control system for an induction motor executes an on-board, dynamic model to estimate rotor resistance and control the torque output by the induction motor. The model includes equations to calculate stator and rotor temperatures and/or resistances based on combinations of voltage and current data, electrical frequency, rotor speed, switching patterns, and air flow rates during operation of the induction motor. The control system updates the model based on feedback collected during the operation of the induction motor, including the difference between the actual observed stator temperature and the stator temperature predicted by the model. The model is updated to converge the predicted stator temperature on the actual observed stator temperature, and corresponding updates are made to the rotor resistance estimations to provide more accurate estimations of the rotor resistance and improve the accuracy of the induction motor torque output.

A method and apparatus are provided for controlling a sensorless alternating current induction motor (ACIM) having a rotor and a stator comprising a plurality of stator windings by applying a plurality of phase shifted voltages to the plurality of stator windings in the ACIM such that two energized stator windings are connected to first and second phase shifted voltages to cause rotation of the rotor relative to the stator while a third unconnected stator winding is floating so that a DC bus current and an inducted voltage can be measured from the ACIM and used to compute an estimated rotor speed.

An electric vehicle control device includes a plurality of drive control systems that controls travelling of an electric vehicle. Each of the drive control systems includes an induction motor, an inverter that drives the induction motor, and a controller that controls the inverter. Each of the controllers of the plurality of drive control systems includes a miswiring detector that calculates a torque estimation value on a basis of motor currents and voltage command values and detects miswiring between the induction motor and the inverter on a basis of the calculated torque estimation value and the torque command value.

A method of a control system controls an inductance motor in a device that may include an impeller using a pressure compensation control system. The control system may be implemented in a respiratory pressure therapy device. The control system may include a sensor configured to provide a pressure signal indicative of the pressure of a flow of fluid produced by the device. A measured pressure may be compared to a set pressure to determine a pressure error. A slip frequency may be adjusted as a function of the pressure error in an attempt to eliminate or minimise the pressure error.

A motor control device according to an aspect of the present disclosure controls a motor by switching between speed control and position control, and sets a maximum voltage applied to the motor during the position control to lower than a maximum voltage applied to the motor during the speed control.

A rotary current machine system and method for controlling an electric rotary current machine, in particular an induction machine, having a rotor, a stator and at least two phase windings is disclosed. At least one electrical signal, in particular a voltage signal, is applied to at least one phase winding, preferably all phase windings, of the rotary current machine, and the current waveform in the at least one phase winding is measured. An intermodulation signal component, induced in the rotary current machine by slotting effects and magnetic saturation effects, which is determined from the current waveform measured in the at least one phase winding, is used for controlling the rotary current machine.