Note: In the figure, the fan is the output link, and the speed is controlled by the inverter to realize variable air volume and constant pressure control. The frequency converter accepts the signal of the PID regulator to control the speed of the fan. After the controller synthesizes the given signal and the feedback signal, the PID adjusts and outputs the operation frequency command to the inverter. The pressure sensor monitors the tuyere pressure and converts it to control its acceptable analog signal for adjustment.
2, the system works
The frequency conversion speed control and the constant pressure supply air control are finally realized by adjusting the fan speed, and the fan is an air supply execution unit. The constant wind pressure achieved by speed regulation is determined by the characteristics of the fan. The characteristics of the fan are shown in the figure below. In the figure, the horizontal axis represents the air volume of the fan Q and the vertical axis represents the pressure P. EA is a constant pressure line, and n1, n2,... nn are the air volume-pressure characteristics at different speeds. It can be seen that under the speed n1, if the opening degree of the control valve makes the air volume decrease from QA to QB, the pressure will reach point B along the n1 curve. Obviously, reducing the air volume increases the pressure at the same time. If the rotation speed is from n1 to n2, the air volume will reduce QA to QC, and the pressure will not change. Therefore, under the premise that the wind pressure can be kept constant in a certain range, the air volume can be adjusted by changing the rotation speed without changing the wind pressure. This characteristic shows that the constant pressure supply can be completed by adjusting the fan speed, changing the outlet pressure, changing the air volume, and stabilizing the pressure on the constant pressure line.
Second, 250KW fan frequency conversion energy-saving transformation program and function
1, the current status of your plant fan operation
There is one existing fan, supporting motor is 250KW, working voltage is 380V, current is 460A. Now it adopts valve adjustment to control the supply of air and pressure. This adjustment method is inconvenient and wastes a great amount of electric energy, which easily leads to the damage of valves and fans.
After many years of energy-saving renovation of pumps and fans in the chemical and tire industries, our company has accumulated rich experience and has strong technical strength.
2, reconstruction program
A 280KW Senlan inverter is used to control a 250KW fan.
3, system function
A. The wind pressure is arbitrarily set, the wind pressure is stable and there is no fluctuation
B. Soft start soft stop, no impact on the power grid, no power expansion
C. Extend the mechanical life of the fan
D. Phase loss, undervoltage, overcurrent, overload, overheating, and stall protection
E. Save energy, quick recovery of investment
Third, the use of fan frequency conversion energy-saving analysis
1, the actual operating power (I real = 350A)
P transportation = √ 3UICOS ω = √ 3 × 380 × 350 × 0.85 = 196kw
W=196×320×24=1505280kwh
Note: Calculated by 320 days a year
2. Automatic control of energy saving speed A Theoretical basis Because the fan is a typical square torque load type, its power (shaft power), torque (pressure), and speed (wind flow) satisfy the following relationship (similarity theorem):
P = P axis = QH
Q'/Q=N'/N then Q'=QN'/N
P'/P=(N'/N)3 then P'=P(N'/N)3
Speed ​​formula of asynchronous motor n=60f(1-s)/p
Where: N, Q, H, P - rated speed of fan, air flow, shaft power
N', Q', H', P' - rated speed of the fan after speed regulation, water volume, shaft power B. Benefit Analysis Based on your plant load (80% throttle opening) and our company's experience, it is estimated that The actual operating speed of the plant is 0.7 to 0.94 times the rated speed, that is, the frequency changes from 35HZ to 47HZ. To ensure the reliability and accuracy of the data, we take f=45HZ to calculate:
P'=(45/50)3×196=142kw
W'=142×320×24=1090560kwh
Saving electricity for W section = = 399840kwh
Economic benefits: 399840×0.60=248832 yuan Note: The electricity fee is calculated at 0.6 yuan per degree
Fourth, Senlan inverter features
1, with superior protection features - with over-current, over-voltage, short circuit, grounding, undervoltage, overload, overheating, phase loss and external alarm protection
2, working environment temperature is -10 degrees to 40 degrees, humidity 95%
3, the inverter overload capacity is 120%, overload time is 1 minute
4. When the inverter runs under the maximum load, the noise at 1m of the motor is not more than 65dB, and the motor has no obvious vibration.
5. The inverter has strong resistance to power supply shock and good electromagnetic compatibility. It has no electromagnetic influence and impact on the nearby instruments and meters.
6, the inverter performance is excellent, long-term stability, no fault work