Application of the hottest frequency converter in

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Application of frequency converter in cement machinery

frequency conversion speed regulation technology is increasingly widely used in China's cement industry. In many links of production process that need speed regulation, such as rotary kiln, single cooler, feeder, batching system, fan, water pump, etc., it has become an inevitable trend to replace voltage regulation, slip regulation and DC regulation with AC variable frequency regulation

in the cement grinding process, the particle size of the material into the ball mill has a great impact on its unit hour output. As an important way to improve the unit hour output of the mill and reduce the power consumption of grinding, the pre crushing process has attracted the attention of many cement enterprises. According to the process requirements, the discharging of the cement shaft kiln lasts for 2 ~ 3 minutes each time, with an interval of 2 ~ 3 minutes. However, at present, the crusher in almost all cement enterprises is in the state of constant speed operation at power frequency and operates continuously for 24 hours, resulting in a huge waste of electric energy and affecting the service life of the motor and crusher. On the other hand, because the crusher has great inertia, it is not easy to start and stop frequently, so even if the frequency converter is used, it is difficult to solve the protection circuit action caused by the pump rise voltage generated during the braking of the system, so that the system cannot work normally

according to the above characteristics of the system, a series of frequency converters are used to realize the frequency conversion speed regulation and soft start of the crusher; The regenerative energy feedback unit is used to overcome the excessive pumping voltage generated in the braking process of the crusher; The logic closed-loop control of the system is realized by PLC, so that the work of the crusher is synchronized with the discharging of the shaft kiln, and the intermittent operation is realized. Thus, while improving the quality of process control, the electric energy is saved to the greatest extent and the production cost is reduced. The results of on-site debugging and operation show that the system operates reliably, and the power saving rate can reach more than 60%

the above system has been put into actual operation in a cement plant. The system automatically realizes the starting and braking operation according to the feeding signal, and the running speed of the crusher is continuously adjustable. The motor can realize frequent soft start and basically no start. The four core enterprises controlled by s'an aluminum will also successively set up and operate in Jiangnan industrial concentration area. Petra shield composite material is made of spectrum fiber, with dynamic current impact and sufficient starting torque. Under the condition of variable frequency operation, if the frequency converter suddenly fails, it will automatically switch to the "power frequency" state to continue operation, and send out audible and visual alarm signals (internal optional). According to the requirements of on-site working conditions, the given frequency of variable frequency operation when there is a discharge signal is set to 43 Hz, the operating current of the system is 27 A, and the operating voltage is 280 v. the performance of the modified system is different, and the average annual power consumption is 57000 degrees. According to the on-site records, the working frequency of the system before the transformation was 50 Hz, the operating current was 32 A, and the operating voltage was 400 V. The introduction of pingru flame retardant PPO series and flame retardant pc/abs series products consumed 194200 kwh of power every year. The electricity saving rate after transformation is 70.6%. The outstanding advantages of this system are as follows:

1. The drive system of cement clinker crusher is reformed by using frequency conversion speed regulation technology, which meets the characteristics of low-speed and intermittent operation of crusher, ensures the quality of process control, has obvious energy-saving effect, and is conducive to extending the service life of crusher and motor

2. The energy feedback control technology is used to overcome the pumping voltage caused by the large inertia of the crusher, which effectively ensures the safe operation of the frequency converter. In addition to more than 20 protection functions and fault self diagnosis functions of frequency converter and energy feedback device, the system also adds motor overheating, control circuit protection and alarm

3. The programmable controller PLC is used to realize various logic control, automatic control of frequency converter startup and braking, manual/automatic, power frequency/frequency conversion, fault self switching and other functions, making the system control flexible and convenient with complete functions

Case 4 Application of frequency converter in compressed air system of paper mill

compressed air is often used in pneumatic pressure lifting device of paper machine department and press department, blanket correction device, air cushion headbox, paper guiding equipment, coating air knife, various pneumatic instruments and regulating devices, etc

in the compressed air system, the main equipment includes air compressor, air storage tank, pressure reducing valve, air filter, steam water separator and safety valve, etc. the pressure on the paper machine usually needs to be about bar. In most paper mills, more than two air compressors are operated in parallel, and then the pressure is kept constant through the air tank

because the compressor has a large power and the control pressure is generally adjusted by loading or unloading, the motor is always in full speed operation. Practice shows that this control method consumes a lot of energy and wastes seriously. Therefore, at present, it has tended to use one frequency conversion and multiple power frequencies to control the compressor unit and form a pressure closed loop

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