Abstract: As an electronic technology, frequency conversion technology significantly improves equipment efficiency, makes operation more convenient, saves energy, and brings considerable economic benefits, thus it is widely used in various fields. This paper discusses the economic benefits and returns of using frequency converters in boiler fan control systems, and finally summarizes the advantages of using frequency converters in boiler fans. Keywords: frequency converter; frequency conversion technology; boiler fan; economic benefit[b][align=center]Applications of Frequency conversion technology on boiler fan LI Guo-ping, HU Ming (Harbin TaiPing heat supply Co. Ltd. Harbin, 150056, China)[/align][/b] Abstract: As a kind of electronic technology, Frequency conversion technology's application makes the equipment more effective, operation much easier, consumption of energy less and it also brings more economic benefits. Therefore, it is widely used in many fields. The mechanism of frequency conversion used in boiler fan control system was introduced, and the economic benefits were also involved. Finally, it comes to a conclusion of advantages of frequency transformer's application on fan of boiler. Key words: Frequency transformer; Frequency conversion technology; fan of boiler; Economic benefits 0 Introduction The emergence and development of frequency conversion technology has solved the control problems in boiler operation, not only saving energy and reducing operating costs, but also significantly reducing boiler pollution, greatly improving the workload of boiler operators, and providing excellent support for the realization of automated control. 1. Frequency Conversion Technology Frequency conversion technology is an electronic technology. Frequency converters are developed based on frequency conversion technology and can be applied to most motor drive applications. Because they provide precise speed control, they can easily control the lifting, lowering, and speed-changing operation of mechanical transmissions. Frequency converters are frequently used in complex systems, harsh working environments, high loads, and long-term operation conditions. Due to the use of communication methods, configuration and system maintenance can be easily performed via PC, including uploading, downloading, copying, monitoring, and parameter reading and writing. Simply put, a frequency converter consists of a three-winding input transformer, rectifier circuit, synthesizing bus, inverter circuit, synthesizing filter circuit, and control cabinet. For many years, the State Economic and Trade Commission, together with relevant national departments, has been committed to the development and promotion of variable frequency speed control technology, and has made the promotion and application of variable frequency speed control technology a key investment direction for energy-saving technological transformation projects for fans and pumps. 2. Application of Variable Frequency Drives in Fan Control Systems Figure 1 shows a block diagram of a variable frequency drive (VFD) controlling a fan motor system. The air pressure is set through the input terminals of the VFD; the pressure sensor transmits the pressure signal to the VFD; the VFD performs calculations through a pre-programmed procedure, outputting control signals corresponding to different pressures, thereby controlling the motor to change the fan speed to adjust the furnace air pressure. The furnace air pressure is transmitted to the VFD through the air pressure sensor, achieving automatic control. In variable frequency mode, the VFD changes the frequency of the fan motor input voltage, thereby controlling the motor speed. The speed of the motor can be expressed by the following formula: n is the speed, f is the frequency, and p is the number of motor stages (2, 4, 6...). The variable speed motion of the fan is to change the fan curve by changing the fan speed. This relationship can be expressed by a set of formulas: Where, n - fan speed; Q - air volume; P - air pressure; N - power. It is worth noting that: when the air volume formula (1) and (2) are combined, the result is exactly in line with the system curve formula: The air volume and air pressure of the fans used in general usually exceed the actual needs. (Air volume margin 5%-15%, pressure margin 10%-30%), the traditional control margin method mostly uses baffle valves to adjust, and these methods are used to throttle. Although the method is simple, it is actually achieved by artificially increasing the resistance. It not only causes waste, but also increases noise pollution. After the frequency converter is modified, it has the following advantages: (1) Automatic control is realized, opening a new chapter in the automation of boiler operation. It automates the difficult-to-control combustion process and reduces labor intensity. In today's increasingly networked world, compared with ordinary point-to-point hard wire connection, the frequency converter system connected by high-speed communication can minimize system maintenance time, improve production efficiency, and reduce operating costs. (2) Control the starting current of the motor. When the motor starts directly at the power frequency, it will generate 7 to 8 times the rated current of the motor. This current value will greatly increase the electrical stress of the motor windings and generate heat, thereby reducing the life of the motor. Variable frequency speed regulation can start at zero speed and zero voltage (of course, the torque can be appropriately increased). Once the relationship between frequency and voltage is established, the frequency converter can drive the load to work according to WF or vector control. Using variable frequency speed regulation can significantly reduce the starting current and improve the winding bearing capacity. The most direct benefit for users is that the maintenance cost of the motor will be further reduced and the life of the motor will be increased accordingly. (3) Reduce voltage fluctuations in power lines. When the motor starts at the power frequency, the current increases dramatically and the voltage will also fluctuate significantly. The magnitude of the voltage drop will depend on the power of the starting motor and the capacity of the distribution network. Voltage drop will cause voltage-sensitive equipment in the same power supply network to trip or malfunction, such as motors, sensors, proximity switches and contactors, to malfunction. However, after adopting frequency conversion speed regulation, since it can start gradually at zero frequency and zero voltage, it can eliminate voltage drop to the greatest extent. (4) The air volume of the fan can be smoothly and steplessly adjusted, the fan works at the optimal operating point, the operating condition curve is more in line with the system, the fan efficiency can be improved, and the "surging" phenomenon can be avoided. The furnace pressure is stabilized and the working environment requirements are met. (5) Low-speed operation can reduce wear and noise, which is conducive to extending the service life of motors and fans. (6) The energy saving effect is significant. Since the final energy consumption is proportional to the cube of the motor speed, the cost is greatly saved after adopting frequency conversion, the return on investment is faster, and users are willing to accept it. 3. Benefits and Returns In 2002, Harbin Engineering University installed four 02-ton coal-fired heating boilers. Two of these boilers provided intermittent heating 24 hours a day for a six-month heating season each year. The blower power was 37 kW, and the induced draft fan was 110 kW. During boiler operation, the power line experienced significant fluctuations, frequently damaging electrical appliances in nearby school buildings. The induced draft fan airflow was too high; adjusting the airflow using baffles did not change the motor power consumption significantly, resulting in substantial energy waste. Based on these shortcomings, it was decided to install frequency converters. After installing the frequency converter, the fan started smoothly without inrush current and operated stably. According to on-site measurements commissioned by the District Technical Supervision Bureau from Harbin Hongguang Boiler Factory, data was measured for the two adjustment methods of the induced draft fan for comparative analysis, as shown in Table 1. For newly commissioned boilers, when the load is generally below 70% for various reasons, the effect of frequency converter control is more obvious. The Taiping heating project is a new type of project approved by the Harbin Municipal Government. Both the blower and induced draft fans of the two boilers are controlled by frequency converters. The induced draft fan motor is 3500 kW, and the blower motor is 1000 kW. The initial investment in the frequency converters for the two boiler blowers and induced draft fans was 500,000 yuan. Over 2 (X) 5 years, the loads in 2 (X) 15 years were 30% and 10% respectively. Under these conditions, the boilers operated at low loads, and both the blower and induced draft fans operated at low loads. The total electricity consumption for the two heating seasons was 613,725 kWh. If frequency converters were not used, the electricity consumption would be approximately 18000 kWh. It is estimated that 1,186,275 kWh would be saved over the two heating seasons. Based on a price of 0.7 yuan per kWh, the total savings would be 830,000 yuan. Below is a comparison of the actual operating costs of the two boiler system methods: A total of 20,000 yuan is saved annually, with a one-time investment of 400,000 yuan in the control system. The cost is recovered in two years. 4. Conclusion Industrial boiler fans using frequency converters for speed regulation achieve airflow control, offering high stability and reliability, and good adjustment characteristics. Because the frequency converter can adjust the air volume very smoothly and stably, the operator can flexibly control the combustion status, improve the boiler efficiency and reduce the workload. The frequency conversion speed regulation significantly improves the operation of the motor, significantly reduces the maintenance, and greatly reduces the speed change mechanism and control mechanism of the mechanical system. It makes the system more convenient to operate, significantly improves the working efficiency of the equipment, and the system adopts multiple protections such as overcurrent, overvoltage, instantaneous power failure, short circuit, undervoltage, and phase loss, avoiding the direct and indirect economic losses caused by the motor burnout affecting production. More importantly, its energy-saving effect has achieved considerable economic benefits. References [1] Zhang Yanbin. Application Practice of Frequency Conversion Speed ​​Regulation [M]. 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