The power frequency air compressor costs electricity, is there any rescue

The power frequency air compressor costs electricity, is there any rescue

There are many types of air compressors, but their air supply control methods are almost always using loading and unloading control methods. Although this air supply method is simple in principle and easy to operate, it has problems such as high power consumption, easy damage to the intake valve, and unstable air supply pressure.

　　Traditional air compressor air supply system power waste analysis

　　 1. There are two main working states of traditional air compressors: one is the loading state and the other is the no-load state.

　　(1) Power consumption during loading

　　In the loading state, after the pressure reaches the minimum value, the original control method determines that the pressure will continue to rise until the maximum pressure value. During the pressurization process, more heat must be released to the outside world, resulting in electrical energy loss. On the other hand, before the gas above the maximum pressure enters the pneumatic components, its pressure needs to be reduced by a pressure reducing valve. This process is also an energy-consuming process.

　　(2) Power consumption during unloading

　　 In the no-load state, when the pressure reaches the maximum pressure, the air compressor reduces pressure and unloads by the following methods: close the intake valve to make the motor in an idling state, and at the same time vent the excess compressed air in the separation tank through the vent valve. This adjustment method will cause a lot of energy waste. According to calculations, the energy consumption of the air compressor during unloading accounts for about 10% to 25% of the air compressor's full load operation, which is still when the unloading time accounts for a small proportion. In other words, the air compressor is idle about 20% of the time and is doing useless work. Obviously, in the loading and unloading air supply control mode, the air compressor motor has a lot of energy saving space.

2. The traditional air compressor pressure control is the upper and lower limit control. First, according to the minimum pressure requirement of the production equipment, set the lower limit of the air compressor output pressure, which is the pressure at which the air compressor starts to load; then add 1 Pa to the minimum pressure Around, as the upper limit of the output pressure of the air compressor, that is, the pressure at which the unloading starts. The output working pressure of the air compressor will fluctuate between the upper and lower limits. The power consumption of an air compressor is directly proportional to the output pressure. The higher the output pressure, the greater the power consumption. A pressure difference of 1 Pa from the lower limit of the output pressure to the upper limit will consume 7-10% of the total power.

3. In the traditional air supply air compressor system, if there are multiple air compressors running at the same time, the output pressure of each air compressor will fluctuate between the upper and lower limits with the pressure fluctuation of the pipe network, so each machine has more Consumes 7-10% of rated power.

　　4. The different setting of operating parameters in the traditional air compressor air supply system will also cause different air compressor power consumption. It must be set according to the air condition to achieve the most economical operating effect.

　　5. Because the motor does not allow frequent startup of the traditional air compressor air supply system, the motor still runs at no load when the air consumption is low, which wastes electric energy. Frequent unloading and loading results in frequent changes in the pressure of the entire gas network, which cannot maintain a constant working pressure.

The power frequency air compressor costs electricity, is there any rescue?

　　 Air compressor constant pressure air supply system transformation case analysis

　　 1. Introduction to the original gas supply system

　　 Take the two air compressors of a certain plant Sullair that we renovated in October as an example. The original air compressor air supply system uses two air compressors to operate at power frequency. The lower limit pressure is 0.5MPa, and the upper limit pressure is 0.7MPa. According to the production situation, two machines operate at the same time during the day and one at night. The general working condition is that the pressure reaches the upper limit of 0.7MPa after 20 minutes of work, and the pressure drops to the lower limit of 0.5MPa after 5-7 minutes of shutdown. Then restart again, and work in this cycle. The problem is that the working air compressor is operated with power frequency power supply, and the frequent start and stop of the motor will cause great damage to the motor and easily accelerate the aging of the motor.

In addition, the long-term atmospheric pressure supply can easily cause the air pipe to burst. Later, the customer directly adjusted the pressure of the pressure relief valve to 0.5MPa in order to prevent the motor from starting and stopping frequently, so that the motor is always running at full load, and a large part of the electrical energy is also wasted. Reduce the service life of the equipment. According to field observations, the upper limit of the air compressor is set at 0.7 MPa and the lower limit is 0.5 MPa. We actually meet the working air pressure of 0.5 MPa, so we must implement constant pressure air supply and balance the air compressor’s working operation to achieve energy saving purpose.



　　 2. Block diagram of variable frequency and constant pressure air supply system 　　The working process of frequency conversion air compressor is shown in the figure:

The power frequency air compressor costs electricity, is there any rescue?

　　 In view of the many problems in the air supply control mode of the air compressor system, we added two variable frequency speed regulators to the two air compressors for constant pressure air supply control. Use a 160kW universal inverter and a 110kW universal inverter, add a PLC, a touch screen, and an A/D conversion module to carry out energy-saving transformation of the air supply system.

According to the requirements, we designed a very practical solution. We took the pressure of the gas storage tank of the air compressor supply system as the control object, and used the pressure transmitter SP to collect the pressure P of the gas storage tank and convert it into an electrical signal transmission. The PLC self-tuning control instrument is compared with the pressure setting value SV of the touch screen, and the calculation is carried out according to the established PID control mode according to the magnitude of the difference, and the control signal is generated and sent to the frequency converter. The frequency conversion device controls the working frequency of the motor and Speed, so that the actual pressure P is always close to the set pressure value SV. Through the organic combination of frequency converter, pressure sensor and PID self-tuning controller, a closed-loop air supply control system is formed to automatically adjust the output pressure of the air compressor. Make the utilization of each air compressor equal, increase the stability and reliability of the system and pipeline pressure, and facilitate the technicians to control and maintain the equipment.

　　 The constant pressure air supply control system adds manual and automatic functions, automatically switches between day and night operation modes, and retains the original control and protection system. In addition, after adopting this scheme, the air compressor motor can be started by the frequency conversion device from stationary to rotating work, realizing a soft start, and avoiding the start-up inrush current and the mechanical impact of the start-up on the air compressor.

　　3, system configuration

　　 (1) The hardware adopts the products of the top domestic brand INVT:

　　1) Touch screen: 1 VT070-N0CX-N

　　2) PLC: IVC1-1410 1 unit

　　3) A/D module: 1 IVC1-2AD

　　4) Inverter: CHF100A-160G/185P-4 1 unit

　　5) Inverter: CHF100A-110G/132P-4 1 unit

　　 (2) Inverter parameters

　　 P0-01=1: set to 1, the running command is controlled by the external terminal

　　P0-03=50: Maximum output frequency

　　 P0-04=50: upper limit of operating frequency

　　P0-05=25: the lower limit frequency is set to 25Hz

　　P0-07=7: frequency command source

　　P0-11=30: The acceleration time is set to 30S, the specific value is based on the working conditions and production requirements

　　 P0-12=30: The deceleration time is set to 30S, the specific value is based on the working conditions and production requirements

　　Note: Please set the parameters according to actual working conditions, the above parameters are for reference only.

　　 Air compressor system energy saving analysis

　　1. Analysis of power saving rate

1) The air compressor is a constant torque load, that is, the torque is the same at different speeds, but the required power is proportional to the speed, so when the speed decreases, the required power will also decrease, so as to achieve the purpose of energy saving .

2) The pressure setting of the frequency conversion air compressor can be one point, that is, the lowest pressure that meets the requirements of the production equipment can be used as the set pressure. The frequency conversion air compressor will adjust the speed of the air compressor according to the trend of fluctuations in the pressure of the pipe network. , Even eliminating the unloading operation of the air compressor, saving electric energy.

3) Because the frequency conversion air compressor makes the pressure on the pipe network stable, it can reduce or even eliminate the pressure fluctuations, so that all the air compressors in the system run under a lower pressure that meets the production requirements, reducing the pressure upward Power loss caused by fluctuations.

　　4) Since the compressor cannot rule out the possibility of running for a long time under full load, the capacity of the motor can only be determined according to the maximum demand, so the design capacity is generally too large. In actual operation, the proportion of light-load operation time is very high. If frequency conversion is adopted, the working efficiency during operation can be greatly improved. Therefore, the energy saving potential is great.

　　5) Adjustment methods (such as adjusting the valve opening and changing the angle of the blades, etc.), even if the demand is small, the operating power of the motor cannot be reduced. After adopting frequency conversion speed regulation, when the demand is small, the speed of the motor can be reduced, and the running power of the motor can be reduced, thereby further realizing energy saving.

　　6) Most single-motor drive systems cannot be adjusted continuously according to the load. After adopting frequency conversion speed regulation, continuous adjustment can be carried out very conveniently, which can maintain the stability of pressure, flow, temperature and other parameters, thereby greatly improving the working performance of the compressor.

　　According to the first-hand data obtained by statistical analysis, the preliminary budgeted power saving rate is about 20%.

　　2, other advantages after transformation

　　1) It can save a lot of power;

　　2) Using a unique space vector (SVPWM) modulation method;

　　3) Simple operation, with keyboard lock function to prevent misoperation;

　　4) The motor running noise is greatly reduced;

　　5) The air supply pressure is stable, which improves the pressure control accuracy;

　　6) The number of loading and unloading of the air compressor is greatly reduced, reducing the wear of the operating parts of the intake valve;

　　7) With automatic protection functions for overload, overvoltage, overcurrent, undervoltage, and power shortage;

　　 8) Under the premise of ensuring lubrication, it is also of great benefit to the machine, due to the rotation speed.

　　 Most of the time running at lower than the original design speed, the wear of each rotating part is greatly reduced, and the service life of the air compressor is prolonged.

In summary, the variable frequency constant pressure air supply system, which uses PID self-tuning controller and inverter as the core components, has strong practicability. It is a technological innovation in the air supply field, saving expenses, reducing production costs, and Increasing production efficiency, reducing equipment maintenance, and improving corporate image have opened up practical and effective ways.

　　1) Power saving:

　　160kW motor, the operating time is 20 hours a day, 30 days a month, the motor efficiency is calculated at 80%, the electricity fee is 0.6 yuan/kWh, and the power saving rate is 30% according to the analysis.

　　 Monthly electricity savings = motor power × running time × motor work efficiency × electricity cost × power saving rate = 160 × 20 × 30 × 80% × 0.6 × 20% = 9216 yuan

　　2) Payback period: investment ÷ monthly power saving = 63000÷9216 = 6.83 months (about 7 months). Therefore, according to the calculation and analysis of the above working conditions, the cost and investment payback period is about 7 months, the investment period is short, and the return is high. If you use a longer time every day, the recovery cycle will be shortened.

　　3) Indirect economic benefits

Reduce the burden of the main power transmission transformer, increase the margin of the transformer, and thus increase the user's load capacity; extend the service life of the equipment by 20%-30%; improve the safety guarantee of the use, and reduce the equipment maintenance expenditure by 25% —50%; can save working hours 25%-50%.