Application of pressure sensor in air compressor control system

Take a single screw air compressor as an example to illustrate the working principle of an air compressor. The working process of a screw air compressor is divided into four processes: suction, sealing and conveying, compression and exhaust. When the screw rotates in the shell, the screw and the tooth groove of the shell mesh with each other, and the air is sucked in from the air inlet, and the oil is also sucked in at the same time. Because the tooth groove meshing surface rotates, the sucked oil and gas are sealed and delivered to the exhaust port; During the process, the tooth groove meshing gap gradually becomes smaller, and the oil and gas are compressed; when the tooth groove meshing surface rotates to the shell exhaust port, the higher pressure oil and gas mixture is discharged from the body.

The frequency converter can be used to change the air displacement by changing the speed of the screw rotor. When the air consumption changes, the frequency converter changes the speed to adjust the air compressor's air displacement to achieve a constant exhaust pressure and save energy. the goal of.

In the air compressor control system, a pressure sensor installed on the air outlet pipe at the back of the air compressor is used to control the pressure of the air compressor. When the air compressor starts, the loading solenoid valve is closed, the loading cylinder does not act, and the inverter drives the motor to run at no load. After a period of time (the controller can be arbitrarily set, here is set to 10S), the loading solenoid valve opens , The air compressor runs on load. When the air compressor starts to run, if the back-end equipment uses a large amount of air, and the compressed air pressure in the air storage tank and the back-end pipeline does not reach the upper pressure limit, the controller will actuate the loading valve, open the air inlet, and the motor will load Run, and continuously generate compressed gas to the back-end pipeline. If the back-end gas equipment stops using gas, the compressed gas pressure in the back-end pipeline and the gas storage tank will gradually increase. When the pressure upper limit setting value is reached, the pressure sensor will send an unloading signal, the loading solenoid valve will stop working, and the air inlet The filter is closed and the motor runs without load.

When the air compressor runs continuously, the temperature of the main body of the compressor will increase. When the temperature reaches a certain level, the system is set to 80℃ (the controller can be set according to the application environment). The fan starts to run to reduce the working temperature of the host. . When the fan runs for a period of time, the temperature of the main engine drops, and the fan stops when it is lower than 75°C.

At present, the commonly used pressure sensors on air compressors in the market include pressure transmitters made of SM5420 chips from SMI and Honeywell MLH016BSB01B pressure sensors! Such products are mainly used in air compressors and water treatment equipment , Industrial equipment, buildings, HVAC, petroleum, automobiles, etc., OEM factories.

SM5420 characteristic parameters: pressure range 0~100kPa≈15, Psi0~200kPa≈30, Psi0~700kPa≈100Psi overload 3X. Rated pressure electrical performance (25℃) power supply 3.0Vz*maximum 10V. DC input impedance 5000±20%Ω output impedance 5000±20%Ω Environmental conditions Electrostatic damage (ESD)>10kv Working temperature -40~125℃ Physical characteristics Weight ≈0.10g Compatible medium is clean, dry, and non-corrosive gas Technical indicators ( All test values ​​are relative to 22℃, 3V constant voltage power supply) Zero point output ±10mV full scale output 60±20mV linearity ±0.20%FSO hysteresis and repeatability ±0.10%FSO zero temperature coefficient ±0.04%FSO/℃ resistance temperature coefficient 0.30 %/℃ Sensitivity Temperature Coefficient -0.20VV%FSO/℃ Zero Thermal Hysteresis ±0.10%FSO Long-term Stability ±0.20%FSO Dimensions Unit: mm(in) Selection Series Range Package Type NPP-301-100A100kPa(15Psi) SO-8NPP-301-200A200kPa(30Psi)SO-8NPP-301-700A700kPa(100Psi)SO-8 Note: 1. This series only provides absolute pressure type. This product adopts MEMS production technology and high-performance test methods, so as to maximize The limit guarantees its working stability and its superior performance has been guaranteed. It has the characteristics of high sensitivity, good dynamic response, high precision, easy miniaturization and integration. As a result, this product is widely used in demanding industrial equipment!