Application of the hottest AIPA high voltage inver

Application of AIPA high-voltage inverter in the cement industry

I. overview

for a long time, our government has attached great importance to energy conservation. China's "Tenth Five Year Plan" for energy conservation and comprehensive utilization of resources puts forward high-voltage and high-power variable-frequency speed regulation as one of the key energy-saving technologies to be developed, and it is required to vigorously promote the demonstration project of high-voltage and high-power variable-frequency speed regulation

at present, the competition in the cement industry is very fierce. It adapts to a relatively large pull, but the key is the competition of manufacturing costs. The power consumption of motors accounts for nearly 30% of the cost, and the high-voltage motors used to drive fans account for a large proportion of motors. Therefore, it is extremely important to do a good job in reducing consumption and increasing efficiency of motors. At present, many cement plants have a serious phenomenon of fan horse pulling trolley. If the frequency conversion speed regulation technology is used to change the running speed of the equipment to adjust the size of the air volume, it can not only meet the production requirements, but also save electric energy, and reduce the wear of the baffle and pipeline caused by adjusting the baffle and the economic losses caused by frequent shutdown and maintenance. Therefore, the adoption of variable frequency speed regulation technology in the fan of the cement plant can save a lot of energy, improve production efficiency and bring great benefits to the cement plant. According to the specific situation, after the fan adopts frequency conversion speed regulation, the power saving rate is within the range of 30%-50%. Generally, the total investment such as additional costs of frequency converter equipment and other installation can be recovered within about 1.5 to 2 years

II. Problems in traditional baffle adjustment

the traditional adjustment method of fan is to adjust the opening of inlet baffle to adjust the air volume. It is a backward method with poor economic benefits, high energy consumption, serious equipment damage, difficult maintenance and high operation cost. The main problems are as follows:

1 Using wear-resistant modified engineering plastics can provide a lower friction coefficient to reduce the wear rate. When the baffle is adjusted, a large amount of energy is lost in the closure process of the baffle. For fans, the most effective energy-saving measure for extruders as critical processing equipment is to adjust the flow by speed regulation. Since most fans are loaded with square torque, and the shaft power is roughly cubic with the speed, when the speed of the fan and pump decreases, the power consumed decreases greatly. Figure 1 shows the relationship curve between power consumption and air volume when the fan adopts various adjustment methods. Among them, curve 1 is the power consumed by the motor when the output damper is controlled, 2 is the power consumed by the motor when the input damper is controlled, 3 is the power consumed by the motor when the slip speed control is adopted (slip motor and hydraulic coupling), 4 is the power consumed by the motor when the variable frequency speed control is adopted, and the bottom curve is the actual shaft power required by the fan when the speed control is

(i.e. the output power of the motor shaft). It can be seen that among many adjustment methods, the best energy-saving effect is variable frequency speed regulation

2. The medium has a great impact on the baffle valve and pipeline, and the equipment is seriously damaged

3. The baffle moves slowly, which is difficult for personnel to operate manually, and improper operation will cause fan vibration. The damper actuator is generally an electric actuator with large torque, which has many faults and can not adapt to long-term frequent adjustment. The adjustment linearity is poor. It is difficult to form a closed-loop automatic control, and the dynamic performance is not ideal

4. When the asynchronous motor is directly started, the starting current generally reaches times of the rated current of the motor, which has a large impact on the electricity and will also cause the motor to heat up. The strong impact torque has many adverse effects on the mechanical life of the motor and fan. There are also wound motor starting by water resistance, which has the disadvantages of complex equipment and low reliability. In the past, hydraulic couplers were also used in cement plants to regulate speed. The disadvantages of hydraulic coupling device are large volume, large noise, narrow speed regulation range, low efficiency and complex maintenance of oil system

III. advantages of variable frequency speed regulation

1 Variable frequency speed regulation can save a lot of energy originally lost in the process of baffle closure, and greatly improve economic benefits. The variable frequency speed regulation of asynchronous motor is realized by changing the synchronous speed by changing the stator power supply frequency f. in the speed regulation, the slip rate can be kept small from high speed to low speed, so the slip power consumption is small and the efficiency is high. It is the most reasonable speed regulation method of asynchronous motor

from the formula n = 60F (1-s)/p, it can be seen that if the power supply frequency f is changed evenly, the synchronous speed of the motor can be changed smoothly. Variable frequency speed regulation of asynchronous motor has the advantages of wide speed regulation range, high smoothness and hard mechanical characteristics. At present, it can be used for pressure holding stacking test; Suitable products are packed in corrugated boxes for electronics, electrical appliances, wires, gold, bicycles, handbags, food, drugs, footwear, furniture and other factories. Frequency speed regulation has become the most important speed regulation mode of asynchronous motors, and has been widely used in many fields

for centrifugal fans, fluid mechanics has the following principles: the output air volume q is proportional to the speed n; Output pressure h23

is proportional to speed n; Output shaft power P is proportional to speed n; Namely:

q1/q2 = n1/n2

h1/h2 = (n1/n2) 2

p1/p2 = (n1/n2) 3

when the fan air volume needs to be changed, if the opening of the damper is adjusted, a large amount of power will be wasted on the damper and pipeline system resistance. If frequency conversion speed regulation is adopted to adjust the air volume, the shaft power can be greatly reduced with the decrease of flow. During variable frequency speed regulation, when the fan is lower than the rated speed, the theoretical power saving is

e= [1- (n ′/N)] × P × T (KWH)

in the formula: n - rated speed

n '- actual speed

p - motor power at rated speed

T - working time

the above formula provides a sufficient theoretical basis for frequency conversion and energy saving

2. After adopting frequency conversion speed regulation, soft start can be realized, the impact on electricity and mechanical load is greatly reduced, and the service life of motor and fan is extended at the same time. At the same time, after adopting frequency conversion speed regulation, the reactive power of the motor is compensated instantaneously through the filter capacitor of the DC link of the frequency converter, and the input power factor of the frequency converter can reach more than 0.95. Compared with direct power frequency operation of motor, the power factor is greatly improved, especially for low-speed motor. After realizing frequency conversion and speed regulation, the fan often operates below the rated speed, and the wear of the medium on the fan and baffle, the wear of the bearing and the damage of the seal are greatly reduced, reducing the maintenance workload. The vibration and noise of motor operation are also significantly reduced

3. After the frequency conversion speed regulation is adopted, the closed-loop control can be easily formed for automatic adjustment. The 420mA signal output by the regulator is transmitted to the frequency converter. By adjusting the motor speed through the frequency converter, the air volume can be adjusted smoothly, with good linearity and fast dynamic response, so that the equipment can operate safely and stably in a more economical state

III. principle and characteristics of AIPA high voltage inverter

innovert series high voltage inverter (unit series multilevel PWM voltage source inverter) of Shanghai AIPA Power Electronics Co., Ltd. is a direct high voltage output voltage source inverter. It