INVT GD600 VFD for Stainless Steel Straightener Retrofit in China

Stainless steel is now a key material in modern industry. Because it resists rust well, works well in very hot or very cold conditions, and is easy to shape. In recent years, China's stainless steel industry has grown quickly and is moving steadily towards becoming a world leader. 

However, this growth faces two big problems: imported products are sometimes not available, and their prices are often too high. Because of this, using more locally made equipment for processing stainless steel has become necessary. Chinese drive systems need to keep getting better in technology, quality, and service. It will help breaking the control of foreign brands and better meet the needs of China's stainless steel makers.

Customer requirement

The stainless steel straightener is an essential processing machine in stainless steel production. After annealing and cold rolling, stainless steel strips have stress and flatness issues. Only by stretching and leveling with a straightener (sometimes followed by a pickling step) can they become flat, saleable steel coils. 

To address the challenges mentioned above, a stainless steel processing company decided to upgrade its straightener with locally made components, replacing the original imported inverter. This company produces steel coils in various sizes, including thicknesses from 0.24mm to 0.40mm. Therefore, the equipment must maintain extremely stable tension when processing different steel strip types.

Schematic diagram of the straightener equipment

INVT Solution

To meet the customer's requirements, INVT introduced the GD600 inverter solution. Featuring advantages such as precise motor auto-tuning, strong control performance, stable torque limiting, and smooth acceleration/deceleration, it successfully replaced the imported brand.
In this solution, the customer retained their original brand PLC. The INVT GD600 rectifier module communicates efficiently with the PLC via Profinet (PN), enabling fast data reading, writing, and exchange, which saves programming time and reduces worker training costs. A PN communication module is installed on the rectifier to achieve seamless connection with the PLC. Meanwhile, communication between the GD600 rectifier and inverter units uses the built-in standard CANopen interface, reducing the cost of additional communication modules.

 Control diagram

Customer Benefits

1 The multi-drive common DC bus solution improves the system's energy efficiency, achieving energy savings of up to 30%.
2. The GD600 enables localization, reducing procurement and after-sales maintenance costs.
3. Capable of running above rated frequency, it increases the straightener's operating efficiency. It also features a long service life and delivers excellent stretching and leveling results.
4. Standard STO (Safe Torque Off) safety function enhances safety by preventing accidental equipment startup, protecting personnel.
5. Stable torque control algorithms fully unleash the equipment's higher performance, ensuring process stability and reliability.
6. The compact multi-drive design saves cabinet space for the customer and increases flexibility in equipment layout.

Straightener diagram

As the stainless steel market grows rapidly, Chinese-made inverter technology has made big improvements in stability and performance.By using INVT's local solution, stainless steel processors have greatly lowered equipment and operating costs. The equipment runs stably, is highly automated, and meets strict production requirements. This has boosted efficiency, strengthened market competitiveness, and won strong customer trust.Looking ahead, INVT will keep improving our industrial technologies. With reliable technology and products, we will continue supporting the upgrade and replacement of imported equipment with domestic alternatives.

Cabinet diagram 1

 Cabinet diagram 2

Cabinet diagram 3