Meanwhile, Siemens’ Drive Technologies Division said it has introduced the Flender EMPP vertical mill drive, a drive concept that prevents load surges arising from short power supply interruptions and optimizes the transfer of forces between the drive and the mill. In addition, the number of components that may be susceptible to faults is reduced. This in turn increases plant availability, and enables the power range to be expanded to 15 MW. With the current trend in the vertical mill market toward applications in larger production facilities, Siemens said the EMPP vertical mill drive enables applications involving power ratings from 500 kW to 15 MW to be operated with high plant availability. This is made possible by an integral, permanent-magnet synchronous motor supplied by a frequency converter. The omission of a bevel gear stage and coupling enables the high forces to be optimally transferred, with the result that less complex components are required, which increases the efficiency of the mechanical system.
The grinding plate can be precisely controlled via the closed-loop speed control of the frequency converter. This means although different feed materials may be involved, the grinding process becomes more consistent and can be optimized locally. Load surges resulting from short interruptions in the power supply are avoided by means of the electrical decoupling of the drive system, thus ruling out damage to the mechanical components. Rotary oscillations excited by the grinding process can be actively dampened via the drive.
