Other new features of Workbench:
• Sensorless Startup Setup Window New Enhanced Current Plus and Accelerated Graphical User Interface for User Benefits of Parameter Description Visualization
• Workbench project bundled with tools is more versatile, covering a variety of reference design boards
• The link between the Workbench and the technical documentation is enhanced. After entering a new project in the program menu, the user is directed to the technical documentation: Quick Start, User Manual, Developer's Manual and API Reference Manual
• In addition, Workbench has fully supported digital PFC plug-in boards since the last release, and is now able to set power-level AC input ranges to handle implemented safety functions such as overcurrent and overvoltage, allowing users to set up at the drive management level. Threshold
Zero speed control using high frequency injection
Improvements to the new firmware are not limited to the experience and ease of use. Version 4.0 includes a new sensorless control algorithm and the previous version of the "state of the art" BEMF state estimator. The new sensorless control algorithm is called "High Frequency Injection (HFI)" for internal magnetic permanent magnet synchronous motors. (PMSM). In such a motor, the magnet is not mounted on the rotor surface but buried in the core of the rotor. Inductance anisotropy occurs in the internal magnetic permanent magnet synchronous motor. It is not difficult to see this from the relationship between the winding and the quadrant and the straight axis (Lq is different from Ld).
Figure 4: Motor magnetic structure
The high-frequency injection method uses the anisotropy of the magnet structure to detect the angular position of the low-speed and stationary rotors. This sensorless detection technique expands the range of rotational speed detection of the back electromotive force (BEMF) estimator or reverse electromagnetic force detection technology. Since the magnitude of the back electromotive force is proportional to the motor speed, when the motor is stationary or the speed is extremely low, the magnitude of the back electromotive force is too small to be easily detected. A high frequency injection method based on a completely different physics principle can control a motor running at a low speed. The pulsating field is injected into the motor and the electrical angle is calculated using the current in the magnetic structure of the motor. In order to avoid additional torque, the setpoint of the injection frequency must be higher than the fundamental frequency. For example, an X-ray scanning motor is used to detect the electrical position of the rotor relative to the anisotropy of the magnet structure. This method is suitable for the static to low speed phase, works in conjunction with the back EMF estimator, and automatically switches the control method in real time according to the motor speed. This new algorithm will belong to many patented innovations in motor control SDKs that STMicroelectronics offers to its customers, with several advantages:
• Zero speed full torque
• Low speed operation
• Sensorless start without reverse rotation
• The fastest sensorless start
• Sensorless positive (clockwise) reverse (counterclockwise) speed detection
In addition, the solution increases the value of applications that benefit from startup efficiency, including air compressors, low speed operation or reverse rotation (washing machine or industrial automation, electric bicycles or traction motors) and more emerging applications.
