1. Introduction

The air compressor is a device that uses electric energy to compress air as a power source. It is widely used in industrial and mining enterprises. The capacity of the supporting motor is generally large, and most of them are continuously operated all the year round, so the potential for energy saving is great.

At present, the common compressors are piston type, screw type and centrifugal type. No matter which working mode, the gas output per unit time of the compressor is certain. At present, the compressor adopts upper and lower limit control or start-stop control, that is to say When the pressure in the cylinder reaches the upper limit of the set value, the air compressor opens and closes the intake valve through its own pressure or oil pressure. This working mode frequently occurs loading and unloading, and the air compressor and the screw air compressor itself have Greatly destructive.

2. The significance of energy-saving transformation of frequency converter

2.1, saving energy. Energy-saving control compressors Compared with traditionally-controlled compressors, energy conservation is the most practical. The compressor operating conditions supplied according to the gas demand are economical operating conditions, and the actual experience proves that the energy saving rate can reach 15%. the above.

2.2. Improve the accuracy of pressure control. The variable frequency energy saving control system has precise pressure control capability. Match the air pressure output of the compressor to the amount of air required by the user's air system. The output air volume of the energy-saving control compressor changes with the change of the motor speed, which effectively improves the quality of the working condition.

2.3. Extend the service life of the compressor. The inverter starts the compressor from a low speed, and its starting acceleration time can be adjusted, thereby reducing the impact on the electrical components and mechanical components of the compressor during starting, enhancing the reliability of the system and prolonging the service life of the compressor. In addition, energy-saving control can reduce current fluctuations when the unit starts, which can affect the power consumption of the power grid and other equipment. The frequency converter can effectively reduce the peak value of the starting current to a minimum, greatly reducing the maintenance cost and time of the machine.

3. Feasibility analysis of energy saving reform

Principle analysis of frequency conversion transformation. The main outlet pressure is used as the adjustment parameter, and the pressure signal is converted into a 4-20 mA DC signal (or 0-10 VDC voltage signal) through a pressure transmitter, and sent to the inverter PID regulator for comparison with the pressure set value. The difference is calculated by the regulator for PI operation, the output signal is sent to the control system, the output frequency of the inverter is adjusted at any time, the motor speed is controlled, the displacement of the pump is changed, and the outlet pressure of the main pipe is maintained at a set pressure value; If the main pressure increases, it will be adjusted automatically.

4.SINCRC500 vector inverter is applied to energy saving reform of air compressor

4. 1. The main circuit. The input side RST of the inverter is connected to three-phase 380V±15%, and the output side UVW is connected to the three-phase asynchronous motor.

4. 2. Collection of pressure signals. The AI1 analog input of the inverter takes the current signal (4-20mA) of the pressure transmitter at the outlet of the air compressor.

4.3, start and stop signals. The X1 terminal of the inverter is connected to the external running command, and the closing is valid.

4. 4. Fault indication. The inverter has a built-in relay output, and TB/TC is a normally closed contact, which is disconnected in case of failure.

4. The new Corey C500 vector inverter has an internal PID function, which can accurately adjust the pipeline pressure of the air compressor. Soft start and soft stop, the acceleration/deceleration time of the inverter can be adjusted. According to the size of the equipment, adjust the appropriate start and stop time to reduce the impact of the asynchronous motor when starting. The protection function is complete (over 30 kinds of protections such as over current, over voltage and over temperature).

5 Conclusion

With the maturity of frequency conversion technology, the frequency converter has been widely used in the transformation of air compressors. It has been proved that the air compressor adopts frequency conversion control and energy saving effect is obvious, which is worthy of promotion and application.