Problems in the operation of air compressors
Although the main motor adopts Y-△ step-down starting, the current during starting is still very large, and there is a certain starting time. The power consumed during this time cannot be ignored. In addition, the impact of large currents at startup can affect the stability of the grid and the operational safety of other electrical equipment.
#Main motor often works at full load, but energy is wasted on the outlet valve, which is non-economical operation and wastes power.
#Main motor power frequency operation causes the air compressor to operate with great noise.
#The main motor power frequency starting equipment has a large impact, and the motor bearing wears a large amount, so the mechanical quantity during the maintenance work of the equipment is large.
When the unloading operation is running, part of the current is not useful, but the idle loss of the machine at the rated speed. Although the mechanical adjusting device can also perform the pressure regulating function, the pressure regulating precision is low and the pressure fluctuation is large; the compressor always works at the rated rotating speed, and the mechanical wear is large and the power consumption is high.
Air compressor frequency conversion energy saving principle
Since many air compressors operate in a loading and unloading mode. The motor idling during unloading, resulting in wasted energy. The frequency conversion control controls the air volume per unit time of the air compressor by changing the rotation speed of the motor, thereby achieving the pressure of the control pipeline.
The control principle is: the pressure value of the pipe network measured by the pressure transmitter is compared with the set value of the pressure, and the deviation is obtained, and the frequency value of the frequency converter acting on the asynchronous motor is calculated by the PID regulator. The inverter outputs the AC of the corresponding frequency and amplitude to adjust the rotation speed of the motor. The air compressor outputs the corresponding compressed air to the gas storage tank to change the pressure until the pipe network pressure is the same as the given pressure value.
Benefits of air compressor conversion after frequency conversion
Energy saving. Compared with traditionally controlled compressors, inverter control compressors have the most practical energy savings. Compressor operating conditions based on air demand are economical.
Reduced operating costs. The operating cost of a conventional compressor consists of three items: initial purchase cost, maintenance cost, and energy cost. The energy cost accounts for about 77% of the operating cost of the compressor. By reducing the energy cost by 24.3%, coupled with the reduction of the impact on the equipment after the frequency conversion start, the maintenance and maintenance volume will also be reduced, so the operating cost will be greatly reduced.
Improve the accuracy of pressure control. The variable frequency control system has precise pressure control capabilities. 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 inverter controlled compressor changes as the motor speed changes. Due to the improved accuracy of the variable frequency control motor speed, it can keep the system pressure variation of the pipe network within the range of 3 psig, that is, within 0.2 bar, effectively improving the quality of the working condition.
Extend the life of the compressor. The inverter starts the compressor from 0Hz, 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, the variable frequency control can reduce the current fluctuation when the unit starts. This fluctuation current will 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.
Reduces the noise of the air compressor. According to the working conditions of the compressor, after the frequency conversion speed regulation is reformed, the running speed of the motor is obviously slowed down, thus effectively reducing the noise of the air compressor during operation. Field measurements show that the noise is about 3-7 dB lower than the original system.
Inverter transformation requirements
Design requirements: The operating state of the main motor inverter keeps the outlet pressure of the gas storage tank stable, and the pressure fluctuation range does not exceed ±0.01MPa; keep the original power frequency control system to ensure that the inverter has abnormal protection, you can cut into the power frequency directly. Does not affect the production; in the case of a small amount of gas, the inverter is running at low frequency or entering a sleep state, so that the motor winding temperature should not exceed the allowable range.