Application of VFD in Industrial Washing Machine

Industrial washing machines refer to washing machines used in hotels, restaurants, laundromats or factories for washing large quantities of clothes. They have the characteristics of large washing capacity, good effect, low cost, high efficiency and low pollution. In recent years, industrial washing equipment is mainly water washing equipment, and the application of frequency converters has become more and more popular. Therefore, frequency converters have brought a new technological revolution to industrial washing equipment, from the earliest non-adjustable semi-automatic washing machines to Two two-speed motors are used to realize the four-speed fully automatic washing machine. The key to the entire washing control of industrial washing machines has finally developed into a modern washing machine that can realize multi-stage speeds with only one motor. It has a very smooth torque when washing at low speed and a high spin speed when spinning. Due to the large load, a large resistance motor is used in order to obtain a large starting torque, and a braking device is also required during deceleration. With the development of high-power switching device manufacturing technology and computer control technology, the use of frequency conversion to control motors has penetrated into various electric drive systems.

If industrial washing machines are classified, they are mainly divided into water washing machines for washing white clothes such as shirts and sheets, and dry cleaning machines for washing colored clothes such as suits and skirts. The washing machine relies on the combination of water temperature, steam and detergent to decontaminate; while the ten-washing machine uses the penetration and extraction of organic solvents such as vinyl chloride petroleum to remove dirt.

The washing process generally consists of washing, rinsing, uniform distribution, drainage, solvent removal and dehydration. In order to cooperate with these washing processes, the injection of water, heating and solvent washing post-processing agent, as well as the series of program operations such as drainage and drying are all completed by the microcomputer controller.

For the washing machine drum, the washing and rinsing process is the frequent forward and reverse operation process, the dehydration is the process of high-speed operation to throw out the water in the clothes, and the uniform drainage process is to discharge the washing water in the drum and distribute the clothes evenly around the drum. the balancing process. Therefore, the speed range of the drum is very wide. When washing and rinsing, the drum is about 2050rpm, the output of the frequency converter is 513Hz, and the drainage is evenly distributed. The control of the rotation speed of industrial washing machines usually uses multiple step-change motors or several standard motors to switch repeatedly through clutch pulleys and forward and reverse switches. To achieve different dynamic torques, a special high-resistance motor is used, and a braking device is also required when decelerating. However, in this way, the driving device will be very complicated, and it is not easy to be trusted. Moreover, with the upgrading of clothing texture and the diversification of detergents, it is difficult to meet the requirements of the original 12-stage speed change in terms of washing, rinsing, uniform distribution and dehydration.

The use of frequency converter basically solves this kind of problem. The frequency converter can use a motor to adjust the speed from low speed to high speed in a wide range, and the transmission device can be made very small, and the control performance and operation performance are greatly improved. For this reason, silent frequency converters have been adopted for a period of time. However, this kind of frequency converter has many disadvantages such as difficulty in instantaneous current control and poor current waveform, which leads to low torque efficiency, and has to increase the capacity of the frequency converter to supplement the lack of torque during low-speed operation. Recently, due to the emergence of high-speed switching insulated gate bipolar transistors, the inverter can control the switching frequency between 1052, which not only achieves low noise, but also greatly improves the performance shortcomings of the inverter. To put it simply, it is a kind of fixed frequency that is used very well, such as fans, pumps, mechanical rolling mills, elevators, frequency conversion air conditioners, etc.

When the asynchronous motor is used for variable speed transmission, it is necessary to properly control and adjust the supply voltage and current frequency according to the characteristics of the motor. but. The performance and application of speed regulation characteristics obtained by adopting different control methods are different. There are two types of inverter control methods, open-loop control and closed-loop control. As an open-loop control, there are control methods; closed-loop control has a slip control method and a vector control method. At present, inverters with various control methods have been commercialized, and users can choose the most suitable inverter according to the purpose and performance required.

Torque characteristics of industrial washing machines when speed is adjusted. The special mechanical structure of industrial washing machines determines the coexistence of unique items. The weight of the clothes when they contain water and solvents is about the same as when they are dry. The inverter is in a low-frequency and high-load state, requiring constant torque output. When dehydrating, because the water has been discharged, the load torque decreases, which is about the 10202 adjustment curve during washing and rinsing, so that the motor with a frequency higher than the base frequency of 501 is in a constant power state, and maintains a high inertia to make the clothes evenly distributed in the drum . Since the output torque characteristics of the motor controlled by the frequency converter are basically consistent with the load characteristics of the industrial washing machine, the frequency conversion drive technology is widely used in the industrial washing industry.