Ouke converter in the drum, induced draft fan aspects of the transformation program

I. Overview:

The appearance of the frequency conversion governor brought a revolution to AC speed regulation. With the continuous improvement and development of frequency conversion technology in recent decades. The frequency conversion speed regulation performance is perfect day by day, has already been applied to the alternating current velocity modulation in different fields by the engineering and technical personnel of different disciplines, different trades extensively. Brought considerable economic benefits to the company and promoted the automation of industrial production. The frequency conversion speed regulation is used for the speed regulation of the AC asynchronous motor, and its performance far exceeds any AC and DC speed adjustment methods in the past. And the structure is simple, wide speed range, high speed accuracy, easy installation and commissioning, perfect protection function, stable and reliable operation, significant energy saving effect, has become the latest trend of AC motor speed.

At present, among the various types of machinery and electrical equipment in various industries in China, the motor matching the blower pump accounts for about 60% of the installed capacity of the motor in the country. The power consumption accounts for about one-third of the total electricity generated in the country. It is worth mentioning that most fans and pumps have large horse-drawn carts during their use, and due to changes in production and processes, it is necessary to constantly adjust the flow, pressure, temperature, etc. of gases and liquids. Many units still use the way of adjusting the air damper or valve opening to adjust the flow rate, pressure, temperature, etc. of gas or liquid. This is actually a way to artificially increase resistance, and at the cost of wasting electricity and money, to meet the requirements of process and operating conditions for gas and liquid flow regulation. This backward adjustment method not only wastes valuable energy, but also has poor adjustment accuracy and large valve pipe losses. It is difficult to meet the requirements of modern industrial production and service, and the negative effects are very serious. This issue has long attracted the attention of relevant countries and government departments and companies in the world. Since 1997, the State Economic and Trade Commission, the State Administration of Taxation, the Ministry of Science and Technology, the Industrial and Commercial Bank of China and other ministries have jointly issued documents and used policies and economic interest levers (such as special loans, etc.) to vigorously promote high energy consumption such as fans and pumps. Technical transformation of the equipment.

Second, investment and energy saving:

The initial investment of the variable frequency system makes it easy for investors to feel a sense of high investment risk. This is mainly due to the fact that the frequency conversion energy saving effect is not well understood or the initial investment of the variable frequency system is compared with some traditional speed control methods, such as: hydraulic coupling, The initial investment of the speed-changing device such as the sliding-fork motor, variable-grade, etc. is compared without considering the energy-saving effect and the function of the inverter, and the feeling of the inverter's quality, stability, after-sales service, etc. is still not well understood; When frequency conversion energy-saving systems (devices) are used in various types of speed control systems, their energy-saving effects can be 5-75% for a single device, and the energy-saving effects of the general application of such devices, such as fans and pumps, can be even. To 8-50%, the average value of the upper limit energy-saving effect is generally obtained from practical applications without being influenced by other factors. The authoritative data can be found in the publicly-sold data (books) on the market; through these data, The calculation of some simple investment recovery rates shows that the payback period for frequency conversion energy saving systems (devices) is generally 4-20 months (this is empirical data and authoritative data).

Third, the inverter features:

(1) The speed range is wide, and the speed range of the inverter is very wide to meet the requirements of various speed control devices. The frequency range is adjustable from 0.5 to 400 Hz.

(2) The control accuracy is high, the digital setting resolution of the inverter is ±0.01%, and the analog setting resolution is ±0.2%.

(3) Dynamic characteristics are good, the self-shutdown device IGBT speed is fast on the inverter side, and SPWM is adopted.

(4) The control mode, load voltage and frequency are controlled by the CPU of the inverter, so the adjustment speed is fast and the dynamic performance of the system is good.

(5) The control function is very strong, suitable for a variety of different types of loads and different control systems. It can interface with various frequency setting signals through terminals. Such as: 0 ~ 10V, 4 ~ 20mA. Various operations such as forward and reverse rotation can be controlled through the terminals.

(6) Through reasonable adjustment, torque increase, torque limit function, current limit function parameters, it can meet large starting torque, and the load change during operation will not cause trip and other accidents. The torque calculation CPU of the economizer will automatically meet the requirements of the production equipment by high-speed calculation according to the set parameters and the detected signal.

(7) The protection function is very strong. There are 13 protection functions for the energy saver. Overvoltage, undervoltage, overcurrent, overload, and overheat can be calculated and protected by the computer at high speed, and the cause of the failure can be recorded.

(8) There are abundant options for the energy saver, which makes the system expansion easier. For example, the serial communication card can be easily communicated with the computer and the programmable controller, and parameters can be set or modified on the programmable controller or the computer. , And can control the energy-saving machine operating status and speed given. And can monitor various operating parameters of the economizer, making the complex multi-machine control system easy to implement.

Fourth, the principle of energy conservation:

A fan is a mechanical device that transfers gas. A water pump is a mechanical device that transfers liquid. Both are machines that convert the shaft power of a motor into the mechanical energy of a fluid. The working principle of the two is basically the same.

The shaft power output by the fan motor is:

Pf = QfHf/102ηfηc Qf - air volume; Hf - wind pressure; ηf - fan efficiency; ηc - transmission mechanism efficiency;

The shaft power output by the pump motor is:

Psh = QshHsh/102ηshηc Qsh - water volume; Hsh - lift;

Ηsh - pump efficiency; ηc - transmission efficiency;

According to the principle of fluid mechanics, the fan air flow rate and pump water flow rate are related to the motor rotation speed power. When the air volume and water flow rate are reduced and the fan and water pump speeds decrease, the motor input power is rapidly reduced. The working principle of the blower and water pump shows that: the air flow (flow rate) of the air blower pump is proportional to the speed of the blower water pump (motor), and the wind pressure of the blower and the lift of the water pump are proportional to the square of the speed of the blower pump (motor), and the fan water pump is The shaft power is equal to the product of air volume and air pressure, flow rate and lift, so the axis of the fan pump is

The power is proportional to the third power of the speed of the fan water pump (motor) (ie, the shaft power of the fan and water pump is proportional to the third power of the power supply frequency). The following table:

Frequency f(Hz) Speed ​​N% Flow Q% Head H % Shaft Power P%

50100%100%100%100%

4590%90%81%72.9%

4080%80%64%51.2%

3570%70%49%34.3%

3060%60%36%21.6%

2550%50%25%12.5%

According to the above principle, it can be seen that changing the fan pump speed can change the fan pump power.

For example, if the power supply frequency is reduced from 50Hz to 45Hz, then P45/P50=453/503=0.729, ie, P45=0.729P50, the theoretical power saving is 27.1%; when the power supply frequency is reduced from 50Hz to 45Hz, P40/P50=403/ 503 = 0.512, that is, P40 = 0.512P50, and the theoretical power saving is 48.8%.

V. Installation overview:

At present, the power of the induced draft fan is 280KW, the power of the blower is 132KW, and the adjustment method of the drum and the induced draft fan is the damper adjustment. Drums and induced draft fans occupy a very important position in the process of production and operation; the transformation of the equipment should be to design the best technical renovation program on the premise of ensuring production safety and to make the stability higher than the original power frequency state. the way. The design of the drum and induced draft system is based on the maximum air supply demand (maximum working conditions plus spare), and the operating conditions of the drum and induced draft fan are the same (ie, the maximum air supply demand of the single machine is taken into consideration); In actual use, there are many times when the fan needs to be adjusted according to the actual working conditions. The traditional method is to use the switch damper to adjust, this adjustment method increases the throttling loss of the air supply system, when the fan is started, There is a start-up surge current, and the adjustment of the system itself is also periodical. The adjustment speed is slow, the ability to reduce losses is very limited, and the entire system is working in a fluctuating state. The frequency conversion governor (device) is installed on the blower. It can solve these problems once and for all. DCS can realize automatic adjustment and control. It can make the system work smoothly and stably, and can recover investment through frequency conversion and energy saving. From the general experience of the use of wind turbines, we can know that the load of wind turbines with dampers (air dampers) in the power frequency state during operation is between 15% and 100%; the load is smaller (air dampers) The greater the throttling loss, the no-load loss of the fan motor becomes more prominent, the lower the fan efficiency (Figure 4); and the change to the frequency adjustment method (ie, the way the motor changes the power supply frequency) is almost non-existent Throttle throttle loss and no-load loss of fan motor, and the inverter device adopts soft-start mode, there is no start-up surge current, and the plant power system with limited short-circuit capacity can also increase its safety.

Sixth, transformation plan:

According to the draft fan configuration, special frequency conversion reformation scheme is as follows:

1) Install frequency conversion system on the drum and induced draft fan (as shown below);

2) Set up remote control and local control in two ways;

3) Retain the original power frequency system and its linkage method, and be mutually useable with the frequency conversion system.

Seven: Control principle

According to the working conditions at the site, we use the negative pressure signal of the boiler to adjust the PID mode. When the inverter receives the operation start instruction, the inverter automatically controls the output frequency after comparing the given signal with the feedback signal on the terminal stage (boiler negative pressure signal) according to the PID adjustment control mode to control the rotation speed of the drum induced draft fan to realize the boiler Produce reasonable negative pressure. The following figure shows:

Note: The boiler negative pressure signal is 4 ~ 20mA

Eighth, the method for calculating the amount of electricity is:

1. Before the power-saving system is enabled, both parties shall install a power meter (the power meter must be calibrated by the power department of Pu'er County before installation) and run for 24 hours to calculate the average power consumption per hour of the motor.

2. After the power-saving system is enabled, run for 24 hours, and then measure the average power consumption per hour of the motor by using the meter.

3, the average hourly electricity consumption C = AB

4, such as the current month electricity system operating time is E hours (operation time saving system has a record)

5, then the monthly electricity F = E × C

IX. Cooperation

Due to the relatively large investment in technical reform of the system, our company has the following multiple cooperation methods for your company to choose:

1. Your company will fully invest in technical innovation funds, and your company will enjoy the benefits of electricity saving in full. Our company will be responsible for installation. Payment will be 65% at the end of installation and commissioning, 30% at one month's running, and the company will install the system within one year. Warranty.

2. Our company will invest in technical reforms in full, and the energy-saving proceeds will be 70% enjoyed by our company to recover investment and profits. Your company enjoys 30%. After the company installed the system within one year after the installation, beyond the one-year maintenance cost, our company will bear 70%, and your company will bear 30%.

3. After the company has fully invested in the technical reform funds, your company can buy out after confirming that the system produces economic benefits. The buyout price is the original price before the company recovers all the investment, and can be discounted after recouping the investment (after being put into use For the first two years, the discount is 20% for each year of use, and 15% for the next four years.) Savings before the buyout benefit from my company 70%, your company enjoy 30%. Our company maintains the system within one year after installation. After more than one year, our company will bear 70% of the maintenance cost before the purchase, and your company will bear 30%. After the installation and operation of the system, your company must be responsible for its safety, can not be artificially damaged and stolen, and your company may not arbitrarily change the operating circuit of the system, otherwise all consequences are your company's responsibility. Regardless of the mode of cooperation, our company has the obligation to provide lifelong service to this system. Before installation, we collect the data parameters of the corresponding equipment operation, and systematically design the application engineering of the motor speed regulation and reconstruction according to the field conditions. After the equipment is delivered to the site, our engineering and technical personnel are responsible for installation and commissioning under the cooperation of your company's electrician, and provide technical and operational training for your company's relevant management and technical personnel. After installation, our system has on-site diagnostics at the site of use. Company technicians will arrive at the site within 24 hours after discovering or receiving a failure notification. Within one year, problems occur in the normal operation of the system. We are responsible for free maintenance. In other cases, we will only charge the corresponding maintenance cost. The system installed by our company for technical innovation funds will be regularly maintained by our company before the buyout.

We use a complete service system to support every system we install, from training to technical support. We provide comprehensive service guarantees for each user to ensure the safety and continuous production of users on site.

X. Conclusion

In summary, the application of the motor variable frequency speed control system in the above-mentioned equipment can not only save energy and electricity, but also greatly improve the technology, improve the modernization level of enterprise management, and narrow the gap between the management level of the same industry in the international developed countries. An effective way to reduce production costs and improve competitiveness is also one of the necessary measures to implement a sustainable development strategy.

Therefore, we believe that the application of frequency conversion motor speed regulation in your company's equipment is of great significance.

We sincerely hope that we can cooperate with your company in the energy saving projects of the above equipment and other equipments, and create a better tomorrow with your company.