Beijing Leader & Harvest Electric Technologies Co., Ltd.
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Application of HARSVERT-A
Abstract: Variable frequency adjusting speed technology has been applying in every kind of industries. Shanshui Group Company has applied high voltage VFD in cement industry from 2004. At present, the high voltage VFD is working on kiln back exhaust fans, high temperature fans, kiln head coal mill fans, kiln head surplus fans, raw mill circulating fans and so on.
Keywords: variable frequency adjusting speed, Hydraulic Coupler, variable frequency reconstruction
1 Introduction
Typical application case: from June to July in 2007, HARSVERT sold 18 sets of high voltage VFDs to Shanshui Group. Most of them are applying on high temperature fans, kiln head coal mill fans, kiln head surplus fans, raw mill circulating fans and so on. Two production lines with daily productivity 5000T in Zibo Shanshui Cement Company and Pingyin Shanshui Cement Company. By VFD, the two production lines achieve ideal energy-saving effect.
2 The shortcomings of original hydraulic couplers
1) Hydraulic coupler is mechanical adjusting speed equipment. It has 5-8% speed loss. Power loss is converted into heat, so a great mount of cooling water is needed to cool oil.
2) The oil temperature is above 95 degree in the actual operation, the water of cooling equipment is easy to scaling and plugging, which results in trouble.
3) Because the hydraulic couplers deliver power by hydraulic pressure oil, its speed control is not stable, the power factor and accuracy of speed adjusting is bad.
4) Because of the low efficiency of the whole hydraulic couplers, low power factor, inaccuracy of speed adjusting, big speed adjusting loss, a large amount of maintenance and high costs, energy-saving effect is not significant .
3 Introduction of high voltage adjusting speed system
Asynchronous motor adjusts speed by changing the supply power frequency of stator to realize variable frequency adjusting speed. It can maintain small speed disparity during the process from low speed to high speed, so the small consumption speed disparity power and high efficiency is the most reasonable method of adjusting speed for asynchronous motor.
At present, the variable frequency adjusting speed is main adjusting speed method for asynchronous motor; it is widely used in many fields.
High voltage variable frequency speed adjusting system has many significant advantages as following:
1. A lot of expenditure loss caused by load tailgate or valve adjustment will disappear after VFD reconstruction;
2. The power factor of asynchronous motor rises from 0.85 to above 0.95 after using VFD;
(3) The high voltage VFD has smallest loss and the efficiency of the whole equipment is 97%;
4 The comparison of VFD and hydraulic coupler
(1) Speed adjusting range of HARSVERT-A high voltage VFD is from 0 to100%. Speed adjusting range of hydraulic coupler is from 40% to 95%, and it has 5% speed loss at high speed range. This will affect output power of equipment.
(2) The efficiency of HARSVERT-A high voltage VFD is high in the whole adjusting speed range ( more than 96%), but the efficiency of hydraulic coupler decreases with adjusting speed decreasing, this results in a lot of loss. Energy-saving decreases sharply.
(3) HARSVERT-A high voltage VFD realizes soft-start for motor. It solves start impact problem thoroughly. If needed, motor can start frequently in a short time. Hydraulic coupler can't solve the start impact problem. Motor still starts directly and needs starting device. It also has big start impact and can't start frequently in a short time.
(4) When HARSVERT-A high voltage VFD drives motor, the motor only needs to be separated from original switch and electrical connection cable. Then connect it to high voltage VFD. It is no need to change connection of motor or change any basic mechanism. When hydraulic coupler puts into service, it must be connected in series with motor and mechanical connection axis. Basic equipment needs to be moved and re-casted. These modifications may be not permitted in some sites.
(5) HARSVERT-A high voltage VFD is high-technology equipment with high reliability and free maintenance. Hydraulic coupler is mechanical equipment with oil pipeline, water pipeline and many sets of systems, so it has high failure rate and heavy maintenance, which shortens the effective production time.
5 Variable frequency reconstruction of high temperature fans
Taking VFD on high-temperature fans for example: the production line of daily production 5000t, high-temperature fan motor is equipped with 6kV/2500kW VFD.
According to the load parameters and operation condition provided by cement plant, HARSVERT-A06/300 (rated voltage is 6kV, rated current is300A) is applicable to the plant.
6 Kiln-back high-temperature fans system introduction
Zibo Shanshui Cement Plant and Pingyinshan Cement Production line are hanging with kiln, its circuit system is shown as Fig.1.

Rotary kiln with daily production 5000t has heated steel cylindrical with 4 degree bevel, diameter of
4.8m and length of 74m, various firebrick were inserted in it. Raw materials from pre-heater enter the kiln from the back of kiln. It is mixed and calcined in rotary kiln at high temperature depending on the the kiln rotating, and materials move forward depending on the slope of the kiln and the kiln rotating.
7 Reconstruction introduction
The power and the heat diffusion of high voltage VFD is much. In order to ensure adequate ventilation cooling, Leader&Harvest designs wind duct on the top of VFD cabinet and power cabinet respectively. They connect to outlet as a whole, discharging the heat outside, ensuring the reliable ventilation effect.
8 The statistic of energy saving
We make statistic about the related operation data before and after VFD reconstruction. The part of the data are analyzed and collected as follows:
1) The comparison table between Zibo shanshui cement no.1 and no.2 kiln fans before and after reconstruction.
8 sets of HARSVERT-A VFDs in different occasions as follows:

Applied occasions Motor power (kW) Motor power before reconstruction (kW) Motor power after reconstruction (kW)
Line 1 no.1 circulating fans 1000 790 661
Line 1 no.2 circulating fans 1000 774 681
Line 1 high-temperature fans 2500 2221 1777
Line 1 coal mill fans 630 348 247
Line 2 no.3 circulating fans 1000 830 681
Line 2 no.4 circulating fans 1000 780 632
Line2 high-temperature fans 2500 2420 1866
Line 2 coal mill fans 630 388 257

From above data we see energy-saving efficiency of each kiln system fan after reconstruction.
Running 24 hours a day, 26 days a month, 11 months a year, that is 7392 hours in all, we can calculate the energy-saving capacity and energy-saving of fans.
Taking the calculation of the fans in line 1 kilns for example:
energy-saving power:
yearly energy-saving:
yearly energy-saving:
5669600kW•h×0.5yuan/kW•h=2834800 yuan(USD 416882)
2) Comparison table between line1 and line2 fans before and after reconstruction in Pingyin Shanshui Cement plant:
5 sets of HARSVERT-A VFDs in different occasions:

Applied occasions Motor power Motor power before reconstruction Motor power after reconstruction
Line 1 high-temperature fans 2500KW 1920 1430
Line 1 surplus fans 630KW 455 345
Line 2 high-temperature fans 2500KW 1890 1380
Line 2 coal mill fans 630KW 510 430
Line 2 surplus fans 630KW 425 330

The tightness of Pingyin Shanshui Cement Kiln is better, so energy-saving effect is good, especially for high-temperature fans. Calculating the energy-saving of fans according to data:in the case of daily production 5500t, the current of no.1 kiln high-temperature fans is about 156A, electric consumption power is about 1430kW, which declines about 490kW. In the case of daily production 5500t, the current of no.2 kiln high-temperature fans is about 148A, electric consumption power is about 1380kW, which decline about 510kW.
Running 24 hours a day, 26 days a month, 11 months a year, that is 7392 hours in all, we can calculate the energy-saving of two sets of high-temperature fans.
High-temperature fans in line 1 kiln:
energy-saving power:1920-1430=490(kW),yearly energy-saving:
490 kW×7392h=3622000kW•h,yearly energy-saving:3622000kW•h×0.64yuan/kW•h=2318000yuan
High-temperature fans in line 2 kiln:
energy-saving power:1890-1380=510(kW),yearly energy-saving:
510 kW×7392h=3770000kW•h, yearly energy-saving: 3770000kW•h×0.64yuan/kW•h=2413000yuan (USD 354852)
Another major benefit of variable frequency reconstruction is that it increases the production of kiln system nearly by 19%, and it also improves manufacturer procell.
9 Concluding remarks
At present, the competition of cement industry is very intense, and the key is still manufacturing costs. Electrical energy consumed by motor accounts for nearly 30% of the cost. Power consumption used to drive fans occupies a large proportion for motor, so declining consumption and improving benefits for motor is much of importance. Nowadays high voltage VFD technology is more mature and failure rate is lower. It is an ideal equipment for energy-saving reconstruction in cement plant.

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