The air compressor is composed of a pair of parallel meshing yin and yang rotors (or screws) rotating in the cylinder, so that the air between the rotor teeth continuously produces periodic volume changes, and the air is transported from the suction side to the output side along the rotor axis, realizing the whole process of suction, compression and exhaust of the screw air compressor. The air inlet and outlet of the air compressor are located at the two ends of the shell, and the slots of the yin rotor and the teeth of the yang rotor are driven by the main motor to rotate.
Air compressor frequency conversion transformation plan:
1. Design principles of frequency conversion transformation plan
Based on the problems existing in the original working conditions and combined with the production process requirements, the system after the frequency conversion transformation of the air compressor should meet the following requirements:
1. The motor frequency conversion operation state keeps the outlet pressure of the gas storage tank stable.
2. The system should have two sets of control loops, frequency conversion and industrial frequency.
3. The system has two sets of control loops, open loop and closed loop.
4. One frequency converter can control two air compressor units, which can be switched by a conversion switch.
5. According to the working condition requirements of the air compressor, the system should ensure that the motor has a constant torque operating characteristic.
6. In order to prevent non-sinusoidal waves from interfering with the air compressor controller, the inverter input should have effective measures to suppress electromagnetic interference.
7. When the power consumption is small, the inverter is in low-frequency operation, and the motor winding temperature and motor noise should not exceed the allowable range.
8. Considering the future expansion of the system, the air compressor inverter should meet the requirements of future working condition expansion.
II. Selection of air compressor inverter
We take the BT12S series fan and water pump dedicated inverter as an example:
1. The frequency accuracy of the BT12S inverter: digital setting is ±0.01%; analog setting is ±0.2%. The pressure fluctuation range can meet the design requirements.
2. The system is designed with two sets of main circuits: variable frequency and industrial frequency.
3. The system is designed with two sets of control circuits: closed loop and open loop.
4. The conversion switch can be used to allow the inverter to control one of the two air compressor units at will.
5. The BT12S inverter is suitable for constant torque characteristic loads. The inverter also has the functions of torque compensation and boosting.
6. Installing an input reactor at the upper end of the inverter effectively suppresses the interference of the inverter to the power grid.
7. Installing an output reactor at the lower end of the inverter ensures that the motor temperature noise does not exceed the allowable range during low-frequency operation.
III. Principle of the transformation plan
The pressure closed-loop control system composed of the inverter, pressure transmitter, motor, and spiral rotor automatically adjusts the motor speed, stabilizes the air pressure in the air tank within the set range, and performs constant pressure control on the working process of the air compressor.
The feedback pressure is compared with the set pressure to control the output step of the inverter in real time, thereby adjusting the motor speed and stabilizing the air pressure in the air tank at the set pressure.
IV. Debugging of air compressor frequency conversion system
The main steps of debugging:
1. Connect the inverter to the system.
2. Operate the power frequency bypass.
3. Operate the frequency conversion circuit, including debugging of open-loop and closed-loop control:
Open loop: At this time, mainly observe the frequency increase of the frequency converter, whether the operating sound of the equipment is normal, whether the pressure increase of the air compressor is stable, whether the pressure transmitter display is normal, whether the equipment shutdown is normal, etc. If everything is normal, the closed loop can be debugged.
Closed loop: Mainly based on the speed of the frequency increase and decrease of the frequency converter and the increase and decrease of the air compressor pressure, do not generate pressure oscillation, and pay attention to observe the mechanical resonance point, and jump the frequency near the resonance point.
V. Benefits of air compressor frequency conversion transformation
1. Energy saving
2. Reduced operating costs
3. Improved pressure control accuracy
4. Extended compressor service life
5. Reduced air compressor noise
With the continuous advancement and maturity of frequency conversion technology, it can be gradually incorporated into the transformation of traditional air compressors, so that air compressors will enter the real economic operation era in the near future and become high-efficiency equipment for enterprises. At the same time, this article also hopes to provide some reference and help for those colleagues who are interested in transforming and improving traditional air compressor equipment, and contribute to the continuous progress of our air compressor equipment.