An Effective Step Towards Optimizing Speed Control Systems and Reducing Maintenance Costs
In line with continuous improvement projects and increasing the productivity of rolling mill equipment, the technical experts of Jahan Foulad Gharb Company successfully eliminated the DC motor tachogenerators entirely, replacing them with an armature voltage-based feedback system. This innovative action has increased speed control accuracy, reduced maintenance costs, and improved the operational stability of the production line.
In the rolling section of Jahan Foulad Gharb Company, seven stands are used for beam forming, each powered by an 850 kW DC motor. Precise speed control of these motors plays a vital role in the final quality of the products. Previously, the control system was managed using a potentiometer, an analog display, and a tachogenerator, which regulated the motor speed between 0 and 750 revolutions per minute (RPM) by sending a 0-10 V voltage signal.
Over time, the wear and tear of control equipment, including the old tachos and displays, led to problems such as measurement error, continuous service requirements, voltage induction in cables, and failure of aluminum couplings. Furthermore, supplying new tachos at a cost of approximately 85 million Tomans per unit placed an additional strain on the maintenance department.
Following detailed reviews by the company’s Electrical and Industrial Automation team, an efficient solution was presented to replace the feedback system. In this plan, the motor’s armature voltage was used as the feedback source, allowing the drive to determine the actual motor speed based on its internal calculations. Additionally, a new digital display was installed in the control room for instantaneous display of the motor speed, offering significantly higher accuracy and readability than the previous system.
With the implementation of this plan, motors number 2, 5, and 7 have so far been equipped with the new system, and their trial performance results have been reported as completely satisfactory.
The advantages of this action include:
✓Elimination of the tachogenerator, coupling, and its connecting cable
✓Reduction of speed display and control error
✓Simplification of troubleshooting and drive setup
✓Update of control equipment
✓Significant economic savings in maintenance costs
According to technical experts, this change has not only reduced costs but also increased the accuracy of motor speed control and the stability of the rolling mill line. Based on the achieved results, the complete execution of the plan on other motors is also on the agenda of the Technical and Engineering Unit.
This project was implemented through the initiative and design of Mr. Mohsen Ghorbani, a Power Electrical Engineer and one of the specialized personnel of the Electrical and Automation Unit at Jahan Foulad Gharb Company. His efforts and expertise have played a significant role in enhancing productivity and reducing maintenance costs for the rolling mill equipment.
