3-phase Field Oriented Control (FOC)

Our products and solutions

We offer the entire range of power semiconductors and ICs including discrete IGBTs and power MOSFETs as well as power modules and intelligent power modules (IPM), high-voltage gate drivers and powerful STM32 microcontrollers needed to implement high-efficiency variable-frequency drive (VFD) motor control. To help reduce and simplify the design cycle, we offer a complete ecosystem of hardware – evaluation boards and reference designs – as well as firmware and software libraries.

Direct and Indirect Field-Oriented Control

Conventional direct field-oriented control (DFOC) algorithms provide more precision for torque control than scalar schemes, but require sensors for the speed control of the rotor and the magnetic flux to provide the data for the FOC algorithms. They also face challenges in the dynamic response and the dependence on measuring the parameters in the motor. 

Instead an indirect field-oriented control (IFOC) method estimates the phase angle of the rotor magnetic field flux, eliminating the need for additional sensors but adding to the complexity and the computation time of the control system.

Sensorless field-oriented control

Replacing the sensors entirely in an FOC motor controller reduces the cost and increases the reliability of an AC induction motor, but also increases the complexity and cost of the controller. To replace the sensor, the information on the rotor speed is extracted from the voltages and currents in the stator windings via the motor terminals. This is then fed back into the current control of the motor. 

The dynamic performance and steady-state speed can be determined accurately at low speeds using the parasitic effects. Profiling tools can be used to determine the performance of particular system designs to build a model that can be used for sensorless motor control. 

Applications 

FOC can be used across AC induction motors and brushless (BLDC) motors to improve the control and accuracy of the motors for a wide range of applications from pumps and fans to conveyors, particularly in industrial automation where long-term reliability is essential.