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Application status and development trend of frequency converter in papermaking

1 frequency conversion application of paper machine drive

the effective production capacity of China's paper industry has been growing continuously since 1990, especially since 1995. According to statistics, since 2000, 1/2 of the world's large paper machines have been installed in China

assuming that China's total GDP will increase at an average annual rate of 7% in the coming period of time, and taking the average annual population growth rate of 0.91% in the past 12 years as the future annual net population growth rate, by 2010, China's per capita GDP will reach 13890 yuan, and then the per capita paper consumption will rise from less than 30 kg to 50 kg. It can be predicted that by 2005, the total consumption of paper and paperboard in China will reach 50.2 million tons; By 2010, the total consumption will reach 69million tons

at present, high-end paper machines occupy 33% of the domestic market, and are basically dominated by international paper machinery giants such as Voith, Metso, Andritz, etc. the supply of paper machines for the whole machine will be basically imported

since more than 80% of the transmission equipment of the new paper machine has adopted AC drive frequency converter, the annual installed capacity of the paper machine transmission will be very considerable in the future annual output of 3 ~ 4 million tons

we use the 17 Mechatronics produced by Voith introduced by a factory to drive the screw rod transformation through the reducer and other 1-series transmission head mechanism Taking the installed capacity of the 50000 ton/year paperboard machine as an example, its paper products are double-sided Coated Whiteboard with a width of 4.2m, including four layers, four presses, 10 groups of drying cylinders, one group of cold cylinders, one group of sizing press, three double roller calenders, four groups of air knife coating, one roll paper part, etc., a total of 72 drives, with a design weight of 120 ~ 500g/m2 and a speed of 600m/min. The frequency conversion capacity of the sub drive (that is, 72 paper machine drives) of the paper machine is 5490kw

from this, we can calculate that the general ton paper capacity is 31W, so we can estimate that the annual installed capacity of frequency conversion in the future is about 90000 kW. Based on the calculation of paper machine nclick= "tagshow (event)" href= "tag.php? Name=%cf%b5%cd%b3"> system design 1kw/2000rmb, there is a total transmission market of about 180million RMB. Of course, the inverter brands are basically dominated by major foreign manufacturers abb, Siemens, AB, Yaskawa, etc. In addition, since the current production capacity of all paper machines in China is less than 300000 tons/year, the domestic market share is probably less than 1/4, and the rest will be occupied by foreign paper machine manufacturers

at the same time, we also note that the increase of high-end paper machines will reach the peak in history. The increase of width and the rapid increase of speed have prompted a large number of the latest high-end vector or DTC controlled frequency converters to be used in the installation of new paper machines. At present, there are basically no corresponding mature frequency converters in China, so most of them are owned by imported brands, and the share of domestic brands is less than 5%. Of course, we have also noticed that as China has increasingly become the world's factory, the frequency converters made in China will gradually move towards the high-end paper machines of international paper machine machinery manufacturers (such as Metso Paper and Voith Paper) with localized institutions

the frequency converter currently used in the sub drive of the paper machine must have the following characteristics at the same time:

(1) the speed regulation range is wide, and the efficiency must be more than 90% in the full speed range

(2) the power factor is higher than 0.9

(3) the total distortion of the input harmonic current is less than 3. This material is also used for% of the mobile rechargeable battery of greenpack, a Berlin manufacturer

(4) adopt standard IGBT with high reliability and mature technology

(5) it can reduce the output harmonic component and effectively reduce dv/dt noise and torque ripple

(6) use the communication function to realize the high-speed serial transmission of data. 2 prospects and analysis of paper machine frequency conversion transformation

2.1 prospects of paper machine frequency conversion transformation

while paying attention to the new paper machine capacity, we must also pay attention to the transformation of existing paper machines. According to relevant statistics, China has a production capacity of more than 37.8 million tons, less than one-third of which is more than 50000 tons per unit and more than 100000 tons per paperboard machine. More than two-thirds of the production capacity needs to be invested heavily in LCP manufacturing, of which at least one-third of the paper machines need to partially or completely replace the original transmission parts (including mechanical gearbox and motor transmission) to improve speed or reduce energy consumption

according to the estimated installed power, we can estimate that in the next five years, about 300000 kW of installed power needs to be transformed. According to the calculation of 1kw/1500rmb of the transformation system, there will be a frequency converter market of about 450million RMB. Since the domestic localization transformation project was originally involved, a considerable number of domestic frequency converters will be used. Therefore, this will be a world where domestic frequency converters can compete, and the market potential is huge, which should be paid enough attention to

in the past, SCR DC speed regulation was used in the transmission equipment of China's paper machine division. Due to the existence of slip rings and carbon brushes, the reliability and accuracy were not high, resulting in the mechanical backwardness of the paper machine. The maximum speed was only about 200m/min, which was difficult to compare with the foreign 1000m/min high-speed paper machine

papermaking is a continuous production process, so the continuous and orderly control of the production line has become a bottleneck restricting the quality and output of finished paper. DC speed regulation system plays an important role in the development history of paper machine, but due to the DC motor's difficult maintenance and poor adaptability to the environment, it is mainly shown as follows:

(1) the commutator is seriously worn, and the fault of burning the commutator leads to a long shutdown time

(2) DC motor maintenance is difficult, demanding and expensive

(3) the tachometer generator is easy to wear, resulting in low accuracy of the transmission system

(4) the DC speed control system is complex and difficult to debug, so it is difficult for ordinary technicians to call out a good machine

AC variable frequency speed regulation technology is recognized as one of the most promising AC speed regulation methods because of its excellent speed regulation performance, remarkable power saving and wide applicability in the field of national economy. It not only has the excellent speed regulation performance of DC motor, but also has the simplicity and reliability of AC motor, so it is gradually widely used. From this point of view, the frequency conversion of paper machine segment transmission machinery is the general trend

the frequency conversion transformation of paper machine transmission has very good results, such as improving paper products from the process, increasing production capacity, reducing energy consumption, and extending the shutdown and maintenance cycle

take the transformation of a long paper machine in a factory as an example, it has two divisions: one is the dryer (cadre), and the other is the dryer (wet). According to the process requirements, the paper making speed is 20 ~ 100M/min, and the paper weight is 9 ~ 30g/m2. Generally, the transmission accuracy of the paper machine is required to reach 1 ~ 3. Due to the wide range of speed changes, the minimum quantity is 9g/m2, which requires a higher transmission accuracy of the paper machine. Therefore, the paper machine transmission control scheme closed-loop system is selected

2.2 benefit analysis

(1) energy saving effect analysis

according to the paper machine energy consumption before and after the transformation of the plant, The comparison is as follows:

electric power before transformation:

90m speed P90 =74a 180V + 3 220=13980w=13.98kw (DC drive)

300 days of production per year:

power consumption of the whole machine =300 2413.98=100656kwh

electric power after transformation:

90m speed P90 =1.732 16A 380v=10530w=10.53kw (variable frequency drive)

power consumption of the whole machine =300 2410.53=75816kwh

it is gratifying that the annual power saving =100656-75816=24840kwh

from this, it can be concluded that the actual energy saving after the application of the frequency converter is: 25%

(2) process benefit analysis

before and after the transformation, it can be seen that the operation rate of the paper machine has increased by more than 27% (obtained from the monthly average output, excluding other factors)

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