Air compressors are widely used in many sectors of the national economy and national defense construction, especially in the textile, chemical, power and other industrial fields. They have become essential equipment and are the core equipment in many industrial processes. Providing sufficient air supply pressure for the compressed air required for automated production is an essential element of a smooth production process. The instantaneous pressure drop affects product quality. With the maturity of frequency conversion technology, frequency converters are increasingly used in the field of electrical transmission. The diversity of its control methods, perfect motor protection functions and its unique advantages are currently unmatched in the field of industrial control.
First, the working principle of screw air compressor Screw air compressor working process is divided into suction, sealing and delivery, compression, exhaust four processes. When the screw rotates in the housing, the screw groove and the tooth groove of the housing mesh with each other, air is sucked in by the air inlet, and at the same time, the oil is also sucked in, the oil gas sucked by the tooth groove meshing surface is sealed and transported to the exhaust port; In the process, the tooth gap is gradually reduced and the oil and gas are compressed. When the tooth groove meshing surface rotates to the exhaust port of the shell, the higher pressure oil and gas mixture is discharged from the body.
Second, the composition of the compressed gas supply system and the principle of air compressor control The composition of the compressed air supply system:
The factory air compressed air supply system generally consists of an air compressor, a dryer, a filter, a gas storage tank, a pipeline, a valve, and an air supply device.
Air compressor control principle:
In the plant's air compressor control system, pressure relays installed on the back-end piping are commonly used to control the operation of the air compressor. When the air compressor starts, the loading valve is in a non-operating state, the loaded cylinder does not actuate, the air intake of the air compressor head is closed, and the motor starts without load. When the air compressor starts running, if the rear-end equipment uses a large amount of gas, the pressure of the compressed air in the air tank and the back-end pipeline does not reach the pressure upper limit, the controller acts to load the valve, open the air inlet, the motor load Operation, continuous generation of compressed gas to the back end piping. If the gas is stopped by the back-end gas equipment, the pressure of the compressed gas in the back-end pipeline and the gas tank will gradually increase. When the pressure upper limit is reached, the pressure controller issues an unloading signal and the loading valve stops working. Closed, no-load operation of the motor.
Third, the screw air compressor frequency conversion transformation Comparison of air compressor frequency operation and frequency conversion operation:
Air compressor motor power is generally larger, start-up mode mostly uses no-load (unloading) star-delta startup, loading and unloading methods are instantaneous. This causes the air compressor to have a large starting current at startup, and has a greater mechanical impact on the equipment during loading and unloading; it not only causes the power supply voltage to fluctuate, but also causes a large fluctuation in the compressed air source; at the same time, this mode of operation It will also accelerate equipment wear and reduce the life of the equipment. Because the drag motor of an ordinary air compressor cannot regulate the speed of the motor itself, it is not possible to directly use the pressure or flow rate variation to achieve the matching of the speed regulation output power. The motor is not allowed to start frequently, resulting in the motor still having to use less gas. No-load operation, great energy waste.
The frequency conversion of the air compressor can make the motor achieve soft start and soft stop, reduce the start shock and extend the service life of the equipment. At the same time, due to the variable operating frequency of the motor, the air compressor can automatically adjust the motor speed according to the amount of gas used. The frequent loading and unloading of the motor is reduced, so that the operating power of the motor is greatly reduced, so that the air supply system pressure is maintained constant, and energy saving can be achieved.
Fourth, frequency conversion reforms the design principle According to the original working condition existing problem and combines the production craft request, after the air compressor frequency conversion transformation system should satisfy the following request:
• The motor's variable-frequency operation keeps the outlet pressure of the gas tank stable, and the pressure fluctuation range cannot exceed ±0.02Mpa.
The system should have two sets of frequency control and power frequency control loops.
·According to the working conditions of the air compressor, the system shall ensure that the motor has constant torque running characteristics.
· In order to prevent non-sinusoidal wave interference with the air compressor controller, the inverter input should have effective measures to suppress electromagnetic interference.
· When the inverter is operating at low frequency when the electrical quantity is small, the motor winding temperature and motor noise should not exceed the permissible range.
Wai.
· Production process requirements, after the frequency conversion transformation, reduce the supply pressure of the compressed gas supply system, and change the original high-pressure variable-flow gas supply to
Variable frequency constant pressure variable flow method.
Fifth, the selection of frequency converter
According to the above principles, Mitsubishi inverters are selected and the inverter switching devices are installed. Only one pressure transmitter is required to form a closed-loop control system. The air pressure signal fed back by the sensor is directly sent to the PID regulator input port of the inverter, and the pressure setting can be set using the keypad of the inverter so that the system can meet the above requirements.
SAJ frequency converter features:
· Adopt 32-bit motor control special microprocessor, high precision frequency output
The novel power accumulation function makes it more intuitive and convenient to observe energy-saving effects.
· Built-in RS-485 interface, computer network control. Multi-signal input, built-in simple PLC, automatic control more convenient.
· The carrier frequency is adjustable and silent operation.
·Diversification of control methods and strong versatility.
· Built-in PID adjustment function, closed-loop control simple low-speed rated torque output, stable operation.
The keyboard is easy to operate, and the parameters can be adjusted and set online during operation.
Low-frequency torque output 180%. Low-frequency operating characteristics are good.
·Output frequency up to 600HZ, control high-speed motor
Full-scale detection protection function (overvoltage, undervoltage, overload) instantaneous restart after power failure
·Protection functions such as acceleration, deceleration, and stall prevention during operation
· Deceleration and stop into natural stop, automatic return, DC braking
A variety of inverter operating status parameters display at a glance the control signal and load operating conditions. During the frequency conversion reformation, we will try our best to maintain the integrity of the original equipment main circuit and control circuit, and make no changes to the circuit; this is beneficial to the fact that the compressor can be easily changed back when the inverter is faulty or inspected. The original control mode goes up, which ensures that the air compressor can run under both variable frequency and power frequency conditions.
First, the working principle of screw air compressor Screw air compressor working process is divided into suction, sealing and delivery, compression, exhaust four processes. When the screw rotates in the housing, the screw groove and the tooth groove of the housing mesh with each other, air is sucked in by the air inlet, and at the same time, the oil is also sucked in, the oil gas sucked by the tooth groove meshing surface is sealed and transported to the exhaust port; In the process, the tooth gap is gradually reduced and the oil and gas are compressed. When the tooth groove meshing surface rotates to the exhaust port of the shell, the higher pressure oil and gas mixture is discharged from the body.
Second, the composition of the compressed gas supply system and the principle of air compressor control The composition of the compressed air supply system:
The factory air compressed air supply system generally consists of an air compressor, a dryer, a filter, a gas storage tank, a pipeline, a valve, and an air supply device.
Air compressor control principle:
In the plant's air compressor control system, pressure relays installed on the back-end piping are commonly used to control the operation of the air compressor. When the air compressor starts, the loading valve is in a non-operating state, the loaded cylinder does not actuate, the air intake of the air compressor head is closed, and the motor starts without load. When the air compressor starts running, if the rear-end equipment uses a large amount of gas, the pressure of the compressed air in the air tank and the back-end pipeline does not reach the pressure upper limit, the controller acts to load the valve, open the air inlet, the motor load Operation, continuous generation of compressed gas to the back end piping. If the gas is stopped by the back-end gas equipment, the pressure of the compressed gas in the back-end pipeline and the gas tank will gradually increase. When the pressure upper limit is reached, the pressure controller issues an unloading signal and the loading valve stops working. Closed, no-load operation of the motor.
Third, the screw air compressor frequency conversion transformation Comparison of air compressor frequency operation and frequency conversion operation:
Air compressor motor power is generally larger, start-up mode mostly uses no-load (unloading) star-delta startup, loading and unloading methods are instantaneous. This causes the air compressor to have a large starting current at startup, and has a greater mechanical impact on the equipment during loading and unloading; it not only causes the power supply voltage to fluctuate, but also causes a large fluctuation in the compressed air source; at the same time, this mode of operation It will also accelerate equipment wear and reduce the life of the equipment. Because the drag motor of an ordinary air compressor cannot regulate the speed of the motor itself, it is not possible to directly use the pressure or flow rate variation to achieve the matching of the speed regulation output power. The motor is not allowed to start frequently, resulting in the motor still having to use less gas. No-load operation, great energy waste.
The frequency conversion of the air compressor can make the motor achieve soft start and soft stop, reduce the start shock and extend the service life of the equipment. At the same time, due to the variable operating frequency of the motor, the air compressor can automatically adjust the motor speed according to the amount of gas used. The frequent loading and unloading of the motor is reduced, so that the operating power of the motor is greatly reduced, so that the air supply system pressure is maintained constant, and energy saving can be achieved.
Fourth, frequency conversion reforms the design principle According to the original working condition existing problem and combines the production craft request, after the air compressor frequency conversion transformation system should satisfy the following request:
• The motor's variable-frequency operation keeps the outlet pressure of the gas tank stable, and the pressure fluctuation range cannot exceed ±0.02Mpa.
The system should have two sets of frequency control and power frequency control loops.
·According to the working conditions of the air compressor, the system shall ensure that the motor has constant torque running characteristics.
· In order to prevent non-sinusoidal wave interference with the air compressor controller, the inverter input should have effective measures to suppress electromagnetic interference.
· When the inverter is operating at low frequency when the electrical quantity is small, the motor winding temperature and motor noise should not exceed the permissible range.
Wai.
· Production process requirements, after the frequency conversion transformation, reduce the supply pressure of the compressed gas supply system, and change the original high-pressure variable-flow gas supply to
Variable frequency constant pressure variable flow method.
Fifth, the selection of frequency converter
According to the above principles, Mitsubishi inverters are selected and the inverter switching devices are installed. Only one pressure transmitter is required to form a closed-loop control system. The air pressure signal fed back by the sensor is directly sent to the PID regulator input port of the inverter, and the pressure setting can be set using the keypad of the inverter so that the system can meet the above requirements.
SAJ frequency converter features:
· Adopt 32-bit motor control special microprocessor, high precision frequency output
The novel power accumulation function makes it more intuitive and convenient to observe energy-saving effects.
· Built-in RS-485 interface, computer network control. Multi-signal input, built-in simple PLC, automatic control more convenient.
· The carrier frequency is adjustable and silent operation.
·Diversification of control methods and strong versatility.
· Built-in PID adjustment function, closed-loop control simple low-speed rated torque output, stable operation.
The keyboard is easy to operate, and the parameters can be adjusted and set online during operation.
Low-frequency torque output 180%. Low-frequency operating characteristics are good.
·Output frequency up to 600HZ, control high-speed motor
Full-scale detection protection function (overvoltage, undervoltage, overload) instantaneous restart after power failure
·Protection functions such as acceleration, deceleration, and stall prevention during operation
· Deceleration and stop into natural stop, automatic return, DC braking
A variety of inverter operating status parameters display at a glance the control signal and load operating conditions. During the frequency conversion reformation, we will try our best to maintain the integrity of the original equipment main circuit and control circuit, and make no changes to the circuit; this is beneficial to the fact that the compressor can be easily changed back when the inverter is faulty or inspected. The original control mode goes up, which ensures that the air compressor can run under both variable frequency and power frequency conditions.