Modulated wave stirring reduces energy consumption of electromagnetic stirrers

Electromagnetic stirrers (EMS) are a must for almost every continuous casting machine for long products. They improve steel quality and support a smooth, stable production process. However EMS are the single biggest consumer of electricity in a continuous caster production line. The modulated wave stirring (MWS) system from SMS Concast radically reduces EMS electricity consumption by 30% and more.

Modulated wave stirring (MWS) shapes the electromagnetic field produced by an EMS. Based on advanced process analysis, it modulates the amplitude and frequency (AFM) of the current in the stirrer coils in such a way that the same stirring effect requires less energy input. The modulated wave requires less energy, hence power savings are achieved. With the amplitude and frequency modulation (AFM) the conventional sinusoidal magnetic field is replaced by a multi-frequency magnetic field so that the liquid steel achieves greater turbulence. The temperature distribution thus getting more uniform, the result is a much more efficient electromagnetic stirring effect.

For the EMS current modulation a proprietary algorithm calculates how the conventional sinusoidal current input is to be adapted in its amplitude and frequency (AFM). The main variables for this calculation are steel grades, section size and specific operational inputs.

The figure below explains in more detail, how CONSTIR-MWS is integrated in the overall system. The frequency converter gets set as usual via the human machine interface (HMI) and the metallurgical recipe system. The  controller generates the amplitude and frequency modulation (AFM) set point based on a special algorithm as explained above. These set points are then provided to the frequency converters which generate the modulation. Thus the original EMS system now performs a fast and reliable AFM operation to improve the stirrer efficiency with respect to performance and energy consumption.

Also, the CONSTIR-MWS controller interfaces to the HMI and production recipe system and can be switched-on or switched-off in order to adapt to processed steel grades. As industrial application, CONSTIR-MWS can be retrofitted to any continuous caster using a Mold-, Strand- or Final-EMS, even when existing EMS units are already installed. No additional screens, buttons or mechanical equipment are needed, apart from the CONSTIR-MWS controller. Field application and trials have confirmed that on seven CONSTIRMWS installations the average energy savings are at 35.4%.

Considering that stirrers are often the largest power consumers on continuous casting machines, such power consumption savings are quite impressive and guarantee a very short return on investment (ROI) time. In this way CONSTIR-MWS represents an economical green technology add-on for any continuous casting machine.