The ACS 6000, one of the world's most advanced medium voltage variable speed drives, is being used to overcome several technical challenges facing a new, 5 meter wide steel plate mill at Zhangjiagang Hongchang Plate Co., Ltd., one of China’s leading steel manufacturers located in Jiangsu province near Shanghai.
New plate mill
In 2005 Zhangjiagang Hongchang Plate Co, Ltd increased its annual capacity of rolled steel to 10mt/a by investing in a new 5m wide rolling mill which produces wide steel plates in a variety of grades for use in buildings, marine and oil & gas industries. Use of such wide plates reduces the number of welding operations required in fabrication.
A plate mill is one of the most powerful rolling mills used in the metals industry. Maximum productivity and high product quality are the two key goals of Zhangjiagang Hongchang Plate Co., and to achieve this a control system is needed that can achieve the high speed, accuracy and power demanded by the plate mill process.
ABB supplied two AMZ motors, two ACS 6000 single drives and one ACS 6000 multidrive for Zhangjiagang Hongchang's new plate mill.
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| AMZ motor | ACS 6000 single drive |
ABB drive systems for demanding process control
The large and rapid power variations, from no-load to overload, places a high strain on all components of the electrical system. The material enters the mill at thread speed and is accelerated to a rolling speed of 2 to 3 m/s in a few seconds. As the hot slabs hit the two heavy work rolls with forces of up to 97,000 kN, the natural reaction is for these rolls to rapidly slow down. To negate this effect high torque is required for the work rolls, which is produced by two powerful 10 MW synchronous motors, each rotating a roll in twin-drive configuration. These machines are among the biggest electrical motors in the world.
As the slabs hit the rolls, the motors also need to withstand a short term overload of up to 250%. This requires a maximum power of 25 MW for 10 seconds. The need is to then speed up the rolls as fast as possible and power the slabs through the roll gap to achieve their final thickness in a minimum number of passes – up to 22 in some cases - before reaching their required thickness.
In addition, the speed and torque of the two vertical edger motors - each 1.2 MW plus 250% overload for 20 seconds - is controlled by one ACS 6000 multidrive.
Benefits
Controlling processes with variable speed drives results in optimized product quality and output, and reduced mechanical wear of the driven equipment. Furthermore, it helps minimize scrap, increases process reliability and reduces CO
2 emissions.