STMicroelectronics has a strong product portfolio for motor control applications. Smooth operation and high efficiency promote the development of motor control. The development of field-oriented control (FOC) software for PMSM, PMAC, and induction motors that use high-performance microcontrollers, power transistors, and high-voltage gate driver ICs has met the need for higher efficiency. For lower power applications, the new highly integrated controller / driver IC for stepper motors can achieve smoother operation and higher positioning accuracy for stepper motors.
Three-phase AC induction motor
Three-phase induction motors are brushless motors. The stator is a copper wire winding, and the rotor is usually an aluminum squirrel cage. A typical drive configuration is a three-phase bridge (three half bridges), which can provide three sine wave voltages to the stator. The driver is usually used for higher power applications, and generally consists of a discrete IGBT with a high-voltage gate driver, or a power module that integrates three half-bridges and related gate drive stages. A field-oriented control or scalar (volts / hertz) control algorithm is implemented in the microcontroller that controls the inverter.
Three-phase induction motor vector drive (FOC)
Vector control (ie, field-oriented control, FOC) is a method used by variable frequency drives to control the torque and speed of a three-phase AC motor. In particular, this method means measuring the motor current and then converting it into a coordinate system that rotates with the machine's rotor. In order to complete this reference frame conversion, the rotor position must be measured directly (through the actual speed / position sensor) or indirectly estimated (sensorless method).
Vector control requires HW peripherals to complete this task and more intensive calculations than scalar control. On the other hand, it achieves better dynamic response (such as changes in loading speed control), more accurate mechanical torque adjustment, and more Quiet operation.
Usually, a low-cost 32-bit microcontroller can handle this kind of driver.
Scalar control voltage frequency ratio driver
In a scalar drive, generally only the frequency and the voltage applied to the motor are controlled (control current feedback is not required).
Especially for Φ induction motors, scalar drives usually control the voltage-frequency (V / F) ratio in the on / off speed loop (only in this latter case must the motor speed feedback be controlled). If you know the motor speed information, you can additionally implement sliding adjustment to optimize the motor efficiency.
Although simple (can be performed by 8-bit and 32-bit microcontrollers), V / f control can meet the needs of most applications.
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