Energy consumption analysis and energy saving solu

2022-08-09
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Air compressor energy consumption analysis and energy-saving solutions

1 introduction

air compressors are widely used in industrial production. It is responsible for providing air source for all pneumatic components, including various pneumatic valves. Therefore, its operation directly affects the production process. The types of air compressors mainly include piston type and screw type, but their air supply control mode is almost through finetest II controller, which adopts loading and unloading control mode

2 electric energy waste in motor principle and air compressor loading and unloading gas supply control mode

2 (1) the speed formula of AC asynchronous motor is:

n=60f (1-s)/p

where n motor speed f operating electrical frequency

p motor pole pairs s slip

2 (2) problems of air compressor loading and unloading air supply control mode

2.1 energy consumption analysis

loading and unloading control mode makes the pressure of compressed gas change back and forth between Pmin and Pmax. Pmin is the minimum pressure value, that is, the minimum pressure that can ensure the normal operation of users. In general, the relationship between Pmax and Pmin can be expressed by the following formula:

Pmax = (1 +) Pmin

is a percentage, and its value is roughly between 15% and 30%

the energy wasted by the air compressor under the loading and unloading gas supply control mode is mainly in two parts:

(1) electric energy consumption during loading

after the pressure reaches the minimum value, the original control mode determines that its pressure will continue to rise until the maximum pressure value. In the process of pressurization, more heat must be released to the outside world, resulting in power loss. On the other hand, before the gas above the maximum pressure enters the pneumatic element, its pressure needs to be reduced by the pressure reducing valve, which is also an energy consumption process. String 2

(2) consumption of electric energy during unloading

when the pressure reaches the maximum pressure, the air compressor depressurizes and unloads by closing the air inlet valve to make the motor idle, and at the same time, vent the excess compressed air in the separation tank through the vent valve. This regulation method will cause a great waste of energy. According to our calculation, the energy consumption of the air compressor during unloading accounts for about 10% - 25% of the full load operation of the air compressor (this is still when the unloading time accounts for a small proportion). In other words, the air compressor is idle for 20% of the time and is doing useless work. Obviously, there is a lot of energy-saving space for the air compressor motor under the loading and unloading gas supply control mode

2.2 other deficiencies

(1) adjust the air inlet valve mechanically, so that the air supply cannot be adjusted continuously. When the air consumption changes constantly, the air supply pressure inevitably fluctuates greatly. The accuracy of gas consumption cannot meet the process requirements. In addition, frequent adjustment of the intake valve will accelerate the wear of the intake valve and increase the maintenance volume and cost

(2) the durability of the vent valve cannot be guaranteed by frequently opening and closing the vent valve

3 design of constant pressure gas supply control scheme

in view of many problems existing in the original gas supply control mode, frequency conversion and speed regulation technology can be used for constant pressure gas supply control. When adopting this scheme, we can take the pipe pressure as the control object. The pressure transmitter Yb converts the pressure P of the air tank into an electrical signal and sends it to the PID intelligent regulator. In its modern vehicle model, it is compared with the pressure setting value P0, and according to the size of the difference, it is calculated according to the established PID control mode to generate a control signal and send it to the variable frequency governor VVVF, which controls the working frequency and speed of the motor through the frequency converter, Thus, the actual pressure P is always close to the set pressure P0. At the same time, this scheme can increase the switching function of power frequency and frequency conversion, and retain the original control and protection system. In addition, after adopting this scheme, the air compressor motor can be started by the frequency converter from static to rotating, realizing soft start, avoiding the starting impulse current and the mechanical impact on the air compressor. String 9

4 selection of system components and installation and debugging of the system

3 Active rear spoiler: polar 1 has a standard active rear spoiler (1) installation

the control cabinet is installed in the air compressor room, which is separated from the original control cabinet, but the main wiring with the compressor should not exceed 30m. The wiring of control circuit adopts shielded twisted pair, and the pitch of twisted pair is less than 15m. In addition, the control cabinet is equipped with a ventilation device, and the grounding terminal of the frequency converter must not be mixed with the power grounding. The above measures enhance the stability and reliability of the system

(2) debugging

a) function setting of frequency converter (different working conditions and control modes, function setting may be different)

f0.01=1 set to 1: operation command is controlled by external terminal

f0.08=20 acceleration time: set to 15s, Specific value according to working conditions and production requirements

f0.09=20 deceleration time: set to 15s

f0.05=50 maximum frequency: set to 50Hz (equal to the rated frequency of the motor)

f9.00=0pi control given source selection ∧

f9.01=72% (given pressure value) PI digital given value (100% corresponds to 10kg)

f9.02=0 or PID feedback source selection on December 26

f9.03=0pi adjustment error polarity: set to positive electrode

(3) Other matters during commissioning

add industrial frequency converter, the whole set of transformation device does not change the original control principle of the air compressor, and the original air compressor system protection device is still effective. And power frequency/frequency conversion switching adopts electrical and mechanical double interlocking, which greatly improves the safety and reliability of the system

in the commissioning process, the lower limit frequency was adjusted to 40Hz, and then the temperature rise of the air compressor motor and the oil temperature of the pipeline were monitored for a long time and strictly with an infrared thermometer. The temperature rise of the motor was about ℃, belonging to the normal temperature rise range, the oil temperature basically did not change, and the exhaust temperature fell by 5 ℃. Therefore, 40Hz lower limit frequency operation is very safe for the work of the air compressor unit

5 conclusion

after a series of repeated adjustments, the system finally stabilized at 39 In the frequency range of 5Hz, the pipeline pressure is basically maintained at 0.69mpa, and the gas supply quality is improved. After the transformation, the operation of the air compressor is safe and reliable, and at the same time, it meets the process requirements of factory gas consumption

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