The metal processing industry is very demanding in terms of the electric motors of the production line.
Steel manufacturing consists of the following processes:
This is carried out in an electric furnace and in the ladle.
Used to obtain the intermediate product of the billet.
After obtaining the billet, it is passed through a reheating furnace and subsequently through the rolling mills, i.e. the grinding, intermediate and finishing mills. The temperature at the start of the rolling mill is 1250ºC and at the end 800ºC.
The rolling mill consists of pairs of cylinders that reduce the cross-section of the billet. The mill is controlled automatically, so that the speed of its different boxes increases in the same proportion in which the cross-section was previously reduced. Each pair of cylinders is controlled by an electric motor and its corresponding variable frequency drive. An inappropriate speed would affect the sectioning of the material and, therefore, the product’s final mechanical properties.
Metal rolling mills provide us with the clearest example of how by controlling the operating variables of the motor, we also control the final properties of the product.
A fault in the motors of the rolling mills would lead to process downtime, loss of material and of lots of energy, namely that used by the electric furnaces.
The operating conditions of the motors are very harsh because of the high temperatures of the process, the environmental contamination and the electronically-driven control. These conditions clearly favour the early deterioration of the insulation of the windings.
In this industry online predictive maintenance is key to:
Preventing very expensive, unforeseen downtimes
Controlling, at all times, the condition of the motor and, therefore, of the process
Eliminating manual measurement taking, which is very dangerous for the maintenance man