Variable frequency transformation scheme for good control JK500 air compressor
An empty press description
Air compressor is a kind of equipment that uses motor to compress the gas in the compression chamber and make the compressed gas have certain pressure. As basic industrial equipment, air compressor is widely used in almost all industrial industries, such as metallurgy, machinery manufacturing, mine, electric power, textile, petrochemical, light textile and so on. Air compressor accounts for 15% of the power consumption of large industrial equipment (fans, pumps, boilers, etc.). Because of the reason of structural principle, most air compressors own obvious technical weakness. When the output pressure is greater than a certain value, it automatically opens the relief valve to make the asynchronous motor idle and waste the energy seriously. The asynchronous motor is easily started and stopped and affects the service life of the motor. The power frequency of the compressor is large, the impact of the motor is big, the wear of the motor bearing is large, the maintenance of the equipment is large, and the working conditions are abominable. The noise is large, the degree of automation is low, and the adjustment of output pressure is realized by the opening of the artificial regulating valve, which is slow in adjusting speed, large in fluctuation, unstable and low in precision.
Two system introduction
The frequency conversion electrical system is composed of a JK500 frequency converter, a pressure sensor and other peripheral components.
(1) JK500 uses open-loop vector control to meet the high and low frequency torque output requirements.
(2) the system is controlled by PID, and the whole control process is as follows: the gas demand, the pipe pressure, the difference between the pressure setting value and the return value, the output frequency of the frequency converter, the motor speed of the air compressor, the supply flow of air supply, tends to be stable.
(3) the pressure sensor provides 0-10V (or 4-20mA) signal, as a given value of PID, and input AI from analog input of KE300.
(4) the start and stop signals are given by the central control system, and JK500 can provide analog output signals through the analog output terminal AO, and access to the central control system to observe the pressure fluctuation in real time. At the same time, it can provide fault alarm signal through relay output.
5) the power frequency bypass can be configured to ensure continuity of production.
Three scheme advantages
(1) active power saving, in the condition of reducing the speed of air compressor, active power saving (the meaning of active power saving is that it can save electricity expenses directly and reduce production cost.) Obviously.
(2) to improve the power factor of the net side, the reactive power and energy saving is obvious. The significance of the reactive power saving is to reduce the line loss of the power supply bus of the workshop and reduce the two current of the distribution transformer in the workshop. The saved reactive current can be transferred to the newly installed equipment in the power grid, thus resolving the question of the capacity of the distribution transformer in the workshop after the new equipment is added. Question. At the same time, the reduction of reactive current can reduce the operation temperature rise of the power transformer, thereby prolonging the service life of the power transformer.
(3) stable heavy load start. The JK500 series inverter has good low frequency response and large power margin, which can fully meet the torque requirements in low frequency operation. Therefore, it is fully applicable to "heavy load start".
(4) prolong the life of the machine. The reduction of the speed of the air compressor, the decrease of the running wear of the air pressure pump, and the effect of prolonging the life of the air compressor; at the same time, the leakage of the oil road of the air compressor is greatly reduced and the pressure on the environmental pollution is reduced.
(5) low oil temperature rise and fall, which is a good measure to reduce the working pressure of air compressors under high temperature in summer.
(6) reduce noise. It can significantly improve the working environment and provide effective means for environmental noise pollution control in occupational health management.
(7) superior soft start and soft stop characteristics. The start and stop time of JK500 frequency converter is arbitrarily adjustable (0 ~ 10min), that is to say, the acceleration at start up and the speed of reducing the parking are adjustable. At the same time, in order to start smoothly, it can also match its S type acceleration and deceleration time, which can reduce the impact of the air compressor when it starts and stop to a minimum. It is difficult for other drivers to achieve.
Matters needing attention：
In order to ensure the normality of the air compressor oil circuit, the frequency of the lower limit of the frequency converter is usually limited to 20Hz.