In recent years, competition in the field of home appliances has become increasingly fierce, technological content has been continuously improved, and product quality has also made considerable progress. In the field of refrigerators, with the improvement of refrigeration technology and thermal insulation technology, the technical indicators of refrigerators have been continuously improved. However, from a control point of view, people are not satisfied with the status quo. The current traditional fixed frequency refrigerators use relays to control the start and stop of the press, and cannot adjust the speed. Therefore, there are inherent power consumption, large current impact, large noise, and poor control characteristics. Disadvantages, from the perspective of component reliability, the core control components and drive execution components (compressors) of the entire refrigerator will shorten the life due to power supply shocks and frequent start and stop, but also cannot meet people's expectations of rapid cooling, stable insulation, etc. Control characteristics.

Especially since the 1990s, with the development of human control methods and the reduction of electronic component technology costs, emerging frequency conversion technology has been continuously attracted to all walks of life. Household appliances from air conditioners, washing machines to refrigerators, microwave ovens have also successfully used frequency conversion technology And greatly improve the service life of the product, reduce the cost of use, and improve the satisfaction of the product to the user.

Various fans and compressors driven by AC induction variable frequency motors. This motor is a type of AC induction motor. The difference from ordinary AC motors is that the motor must be run at different frequencies. The design of the magnetic circuit ensures that the motor is Working under frequency has a high efficiency, so that the magnetic field strength will not be excessively saturated and increase the loss.

Brushless DC motor with position sensor, a kind of DC variable frequency motor, this type of motor is divided into square wave drive, sine wave drive and other types, the characteristic is that the motor itself is equipped with a position detection device, such as a Hall element, so from the control As far as the system is concerned, the position and speed information of the motor rotor are directly obtained, which simplifies the control algorithm, but the motor body structure is complex and the cost is slightly lower.

Limited company, engaged in air conditioning development.

DC brushless sensorless motor, a kind of DC variable frequency motor. Similarly, according to the characteristics of the permanent magnet poles of the motor rotor, it can be subdivided into square wave drive, sine wave drive and other types. This type of motor has a simple structure and high efficiency. However, because the position sensor is omitted, which brings certain control difficulty to the controller, the controller must have the function of judging the position and speed of the motor rotor, thereby increasing the calculation burden of the controller.

The use of single chip microcomputer has the advantages of strong anti-interference ability, strong interface ability, low cost, abundant optional resources, and is suitable for the household appliance industry. The disadvantage is that the calculation speed is slow.

The use of DSP has the advantages of fast calculation and is suitable for industrial fields. The disadvantages are weak anti-interference ability, weak interface ability, high cost, and few optional models.

It is implemented in hardware, and selects a special chip for motor control to achieve frequency conversion control. The core control part is only responsible for giving instructions to the control chip. The cost of this solution is difficult to modify, but the reliability is short, and the design cycle is short and the difficulty is low.

It is realized by software. Usually, a control chip or DSP with 6-way PWM output is selected. The algorithm for controlling the frequency conversion object is completed by the control chip. The solution has low cost and strong versatility, but the program volume is large and the development is difficult.

The drive bridge arm uses power to drive discrete components, such as IGBT, MOSFET, etc., and is equipped with isolation and IGBT drive chips. This solution has a low cost, but it takes up a lot of PCB space, debugging is difficult, and the performance and reliability are slightly lower. After the production is mature, it is used when there is a need to reduce costs; it is implemented with an intelligent power module. The cost of this solution is on the low side, but it is easy to use, easy to debug, strong in reliability, reliable in protection function, and rich in optional resources; 1.3 commonly used frequency conversion control software The scheme is suitable for DC brushless square wave drive motors. For motors with position sensors, the motor structure is relatively complex, but the control is simple, and the difficulty of controlling the motors without position sensors lies in starting and judging the phase to generate commutation logic. In terms of aspects, the algorithm is relatively simple compared with the AC frequency conversion technology, and the required resources are relatively small. The disadvantage is that there are inherently large torque fluctuations and relatively large noise. At the same time, the motor is a permanent magnet motor, and the general price will be lower.

It is suitable for DC brushless sine wave drive variable frequency motor and AC induction motor. The former is a special shape magnetic pole permanent magnet motor. The price is slightly lower. The disadvantage of the two is that the calculation is more complicated, the efficiency is slightly lower than vector control, and the resource requirements are more. The advantages are The torque fluctuation is slightly smaller and the noise is smaller.

It is suitable for AC induction motors. The disadvantage is that the calculation is more complicated and more resources are required. The advantage is that the torque fluctuation is small, the noise is small, and the motor price is relatively low.

It is suitable for induction motors for women's flow, etc. The disadvantage is that the calculation is more complicated and more resources are required. The advantages are less torque fluctuation, less noise, lower cost and complicated control. At present, it is rarely used in the home appliance industry.

1.3.5 Direct torque vector control. It is suitable for AC induction motors, etc. The disadvantage is that the calculation is complicated, the demand for resources is large, the advantage is that the torque fluctuation is minimum, the noise is small, the cost is low, and the control is complicated. At present, it is rarely used in the home appliance industry.

2 Application of frequency conversion technology in refrigerators At present, compressors for refrigerators mainly include AC fixed frequency compressors and DC brushless sensorless compressors. The compressor's efficiency and noise performance indicators can meet the requirements of use. In the control scheme of the inverter refrigerator, the square wave drive scheme of the sensorless brushless DC motor is selected, and the drive bridge arm uses discrete components.

The temperature sensing 1 man-machine interface can understand the advantages of the inverter refrigerator from the control scheme of the inverter refrigerator. Usually the control block diagram of the inverter refrigerator is shown as follows: After the user sets the parameters, the controller collects data from the sensor to determine the compressor Control strategy, the corresponding parameters are transmitted to the drive board (mainly the compressor speed parameter) through the communication line, and then the drive board adjusts the press to the required speed according to the requirements, in which the drive board realizes overpressure and underpressure protection of the compressor, Overcurrent protection, low speed start, thereby reducing start current.

The -03N DC inverter compressor realizes the functions of low starting current, overcurrent protection, undervoltage and overvoltage protection, and the compressor is continuously adjustable from 2000rpm to 4000rpm. The refrigerator runs smoothly at low and high speeds, achieving the goals of energy saving and noise reduction.

The improved performance of the control objects of the refrigerator provides a broad design space for the majority of technicians. It can be foreseen that as people have deep understanding of refrigeration and fresh-keeping technologies and use more sensors, more powerful fuzzy control will appear in the refrigerator field. Refrigerators; With the continuous improvement of the technology of compressor manufacturers, there will be various types of inverter compressors with better performance; the design of the controller will also appear with the development of electronic components and the development of control theory. Products; At the same time, in the large-capacity refrigerator, the frequency conversion technology will have better performance.