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Basic situation before transformation
1． basic situation
Baffle opening range
1#induced draft fan
2#induced draft fan
2．Disadvantages of equipment operation before transformation
High speed of motor and fan, heavy load intensity;
Poor adjustment accuracy and inaccurate control;
The electrical control starts directly, the current impact on the power grid is large at the start, and the power supply (grid) capacity is large, and the power factor is low;
The mechanical impact is large when starting, and the service life of the equipment is low;
The electrical protection characteristics are poor. When the load has a mechanical failure, it cannot instantly protect the equipment.
1、 Analysis of the operation of traditional fans
1.1 Wasted electricity
The fan power is 220KW, and the adjustment of the baffle controls the damper. The speed of the fan is constant, and the air volume is controlled by the baffle, resulting in a disproportionate amount of air volume and motor output power, resulting in a lot of energy wastage.
Motor start-up adopts step-down starting mode. During the start-up process, the rush current is 3-4 times higher than the irregular current, which has a great impact on the power grid. Moreover, the operation is complicated, the amount of maintenance is large, the equipment failure rate is high, and the maintenance cost is high, resulting in a large loss of production shutdown.
2、Overview of traditional solutions
Usually in industrial production and product processing manufacturing, fan equipment is mainly used in boiler combustion system, drying system, cooling system, ventilation system, etc., according to production needs to control and adjust the furnace pressure, wind speed, air volume, temperature and other indicators to Adapt to process requirements and operating conditions. The most commonly used control method is to adjust the opening of the damper and baffle to adjust the controlled object. In this way, regardless of the size of the production requirements, the fan must run at full speed, and the change in operating conditions makes the energy consumed by the throttle loss of the damper and the baffle. In the production process, not only the control accuracy is limited, but also a large amount of energy waste and equipment loss. As a result, production costs increase, equipment life shortens, and equipment maintenance and repair costs remain high
Renovation plan design requirements
1、Working principle of inverter
The frequency converter is an electric energy control device that uses the on-off function of the power semiconductor device to convert the power frequency power supply to another frequency. The low-voltage frequency converter mainly adopts the AC-DC-AC method. First, the industrial frequency AC power is converted into a DC power through a rectifier, and then the DC power is converted into an AC power whose frequency and voltage can be controlled to supply the motor. The circuit of the frequency converter is generally composed of four parts: rectification, intermediate DC link, inverter and control. The rectification part is a three-phase bridge type uncontrollable rectifier, the inverter part is an IGBT three-phase bridge inverter, and the output is a PWM waveform, and the intermediate DC link is filtering, DC energy storage and buffering reactive power. The speed of the motor can be adjusted freely through the inverter.
2、Technical parameters of MV300P inverter
2.1 The main technical features of MEGMEET inverter MV300 series inverter:
3、 Energy-saving solutions
3.1 Transformation principle
The energy-saving function of the frequency converter is essentially that it controls the speed of the motor to minimize the unnecessary consumption of the motor and the part of the energy that the process must consume. Taking the fan as an example, the traditional control uses the opening of the damper flap to adjust the air volume. In this case, the motor runs at a constant speed and the output power is also constant, but when the damper is not fully open, There is always energy consumption on the damper baffle. When the inverter is used, the damper is fully opened, and the air volume is adjusted by reducing the speed of the motor. In this case, the motor reduces the air volume by reduc
3 .2 Features and effects of frequency conversion energy saving
The frequency conversion wind control has unparalleled advantages, and the energy saving effect is remarkable.
According to the principles of fluid mechanics, the air volume Q of the fan load is proportional to the speed N, and the required power P is proportional to the cube of the speed N. Therefore, when the air volume is less than the rated air volume, the motor speed is changed, the power is significantly reduced, and it has a significant energy saving effect.
Increased fan efficiency
The working efficiency of the fan is calculated by the following formula:
Where Q is the air volume, n is the speed, and C1C2 is a constant
When the air volume is controlled by the damper, since the speed n is unchanged, and the air volume Q decreases, the efficiency ηp decreases. When the air volume is controlled by the speed, the air volume is proportional to the speed and the ratio (Q / n) does not change, so the efficiency ηp always remains Good condition.
① The power factor on the grid side is improved: when the original motor is directly driven by power frequency, the power factor at full load is about 0.85, and the actual operating power factor is much lower than 0.8. After adopting the energy-saving control system speed regulation system, the power factor of the power supply side can be increased to more than 0.9, and the reactive power can be greatly reduced without reactive power compensation devices, to meet the requirements of the power grid, and the operating costs of upstream equipment can be further saved.
② Reduced equipment operation and maintenance costs: After the energy-saving control system is used for adjustment, the motor and fan / water pump speeds are reduced when the load rate is low due to the adjustment of the motor speed, and the main equipment and corresponding auxiliary equipment such as bearings are worn out earlier Alleviate, the maintenance period can be lengthened, and the operating life of the equipment is extended; and the opening of the damper / valve can reach 100% after the energy-saving control system is reformed, and it does not withstand pressure during operation, which can significantly reduce the maintenance of the damper / valve. During the operation of the energy-saving control system, it is only necessary to remove dust from the energy-saving control system on a regular basis without stopping the machine, thus ensuring the continuity of production. With the needs of production, adjust the speed of the fan / pump, and then adjust the air volume of the fan / pump, which not only meets the requirements of the production process, but also greatly reduces the work intensity.
After adopting the energy-saving control system technology to adjust the speed, the mechanical wear is reduced, the maintenance workload is reduced, and the maintenance cost is reduced.
③ After the speed control device of the energy-saving control system is used, the motor can be soft-started. The current does not exceed 1.2 times the rated current of the motor at the start, without any impact on the grid, and the service life of the motor is extended. In the entire operating range, the motor can ensure smooth operation, reduced losses, and normal temperature rise. The noise and starting current of the fan when starting are very small, without any abnormal vibration and noise.
④ Compared with the original old system, the energy-saving control system has multiple protection functions such as over-current, short-circuit, over-voltage, under-voltage, phase loss, temperature rise, etc., which protects the motor more perfectly.
⑤ Simple operation and convenient operation. Parameters such as air volume or pressure can be given remotely through a computer to achieve intelligent adjustment.
⑥ The system is able to operate normally when the grid voltage fluctuation capability is strong and the voltage working range is wide.
Power before transformation
Power after transformation
1# induced draft fan
2#induced draft fan
The reconstruction of the fan shows:
1、The system operation is very stable after the transformation, the performance of Megamet frequency converter is good, the quality is superior, and there is no interference with other equipment.
2、The energy-saving transformation of the fan using the alternating frequency converter has a simple structure, convenient transformation and obvious energy-saving effect.
3、 After using the inverter, the fan can be started and stopped softly, reducing the mechanical impact of the equipment, extending the service life of the equipment, and reducing the maintenance cost of the equipment.
4、 The frequency conversion speed regulation technology is advanced and mature, which improves the technical content of the equipment.