Fan and water pump inverter

Industry Overview

The blower, induced draft fan and other fan equipment commonly used in industrial equipment are generally motors running at constant speed, and then the air volume is adjusted by changing the damper opening of the fan inlet. The most important feature of the fan is that the load torque is proportional to the square of the speed, and the shaft power is proportional to the cube of the speed, so if you change the fan's constant speed operation to adjust the motor's spot color according to the demand flow, you can save a lot of Electric energy.

Working principle analysis

According to the theory of fluid mechanics, the direct relationship between the power P of the motor, the air volume Q, and the pressure H:

P=K*H*Q/n

Where K is a constant;

N is efficiency.

Their relationship with speed N is:

Q1/Q2=N1/N2

H1/H2=(N1/N2) 2

P1/P2=(N1/N2) 3

Curve 1 in the figure is the characteristic curve of pressure H and flow Q of the fan at constant speed, and curve 2 is the wind resistance characteristic of the pipe network (valve opening is 100%). Assume that the fan has the highest efficiency at design point A. The output air volume Q1 is 100%. The shaft power P1=Q1*H1 is proportional to the area AH10Q1. According to the process requirements, when the air volume needs to be reduced from Q1 to Q2 (eg, 70%), such as the use of regulating the valve method is equivalent to increase the pipe network resistance, so that the pipe network resistance to 2

Curve 3, the system changed from the original operating point A point to point B operation, can be seen from the figure, the wind pressure but increased, the shaft power P2 and area BH20Q2 is proportional to the reduction is not much.

If the frequency conversion speed control method is adopted, the fan speed is reduced from N1 to N2. According to the proportional law of the fan, the Q characteristic of the pressure H box under the speed N2 can be drawn as shown by curve 4, and it can be seen that the same amount of air Q2 can be met. Below, the wind pressure H3 will be greatly reduced, the power P3 (corresponding to the area CH30Q2) is also significantly reduced with the saved power ΔP = △HQ2 is proportional to the area BH2H3C, the energy saving effect is very obvious.

It can be known from the fluid mechanics that the air flow Q is proportional to the primary equation of the rotational speed, and the wind pressure H is proportional to the square of the rotational speed. The axial power P is proportional to the cube of the rotational speed. When the air volume decreases, the shaft power drops a lot when the fan speed decreases.

In theory, when the air volume of the fan drops to 80% and the speed drops to 80%, the shaft power drops to 51% of the rated power. If the air volume drops to 50%, the power P can drop to 13% of the rated power. Of course, Due to the influence of the actual working conditions, the actual energy-saving effect cannot reach the theoretical calculation value. However, when the fan system uses the frequency conversion speed control method to control the air volume and the flow rate, the energy-saving rate can generally reach 20% - 50% to meet the requirements of energy saving and consumption reduction.

Scheme electrical diagram

System scheme advantages

1. It can realize soft start, start and stop smoothly, and has little impact on power grid and mechanical equipment.

2. Accurate control, smooth speed regulation, large speed range, stepless speed regulation.

3, simple operation, low maintenance, low maintenance costs.

4, strong protection, built-in inverter overvoltage, overcurrent, undervoltage, overload, overheating, lack of equal protection