Research On Refrigerator Comperssor High-Voltage Brushless DC Motor And Control System

The general development trend of household electric appliances is low noise, high efficiency, energy saving and intelligent. It has a higher demand for its matching motor and drive system. However, brush DC motor and single-phase induction motor which is used extensively in the current is hard to meet. Along with the rapid development of permanent-magnet material, the power electronic technology and the computer control technology, the application of brushless DC motor is more and more popular. Instead of the mechanical commutation device in brush DC Motor, there is an electronic commutation device in brushless DC motor. It not only keeps the excellent varied speed and control performance, but also gets rid of a series of shortcomings in brush DC motor due to mechanical commutation. Moreover, it has many features, such as simple structure, reliable operation, high efficiency, maintenance-free, high power and torque density. It has very broad market prospects in the area of household electric appliances.Brushless DC motor can replace the single-phase induction motor. It is an ideal drive motor for household electric appliances like refrigerator compressor. General brushless DC motor adopts rotor position sensor to detect rotor position signal and achieve commutation control. However, the existence of rotor position sensor has brought a lot of shortcomings. It limits application range of to a certain extent. More importantly, the environment in the refrigerator compressor is quite bad. The Hall position sensor which is used commonly cannot work normally and reliably. The sensorless control technology makes structure of brushless DC motor more simple and operation more reliable. Thus, the research on refrigerator compressor high-voltage sensorless rare earth permanent-magnet brushless DC motor and control system in this subject has more high theoretical and practical value.This paper summarized research situation and development trend of the permanent-magnet brushless DC motor and sensorless control technology at first. It also overviewed operating principle and characteristics, mathematical models and control method of permanent-magnet brushless DC motor. It discussed commutation process of permanent-magnet brushless DC motor and obtained the current change rule in commutation process based on the analytical method. It studied mechanism and corresponding suppression method of ripple torque in the permanent-magnet brushless DC motor. On this basis, electromagnetic design of the refrigerator compressor high-voltage rare earth permanent magnet brushless DC motor is conducted, and a refrigerator compressor driven machine prototype is developed. On the other hand, the important theoretical issues such as rotor position signal detection, error and that compensation and starting process are analyzed in the sensorless brushless DC motor. After the plan demonstration, the sensorless brushless DC motor exclusive control chip ML4425 is used as a dominant chip. The controller based on the ML4425 is designed and produced. The on-line debugging of motor and controller is conducted, and major test waveforms and results are obtained.