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Danfoss solution to be implemented in the Sagrex Lemay quarry, Belgium

Published by , Deputy Editor
World Cement,

Limestone crushing represents a large proportion of the electrical energy consumed by the Sagrex Lemay quarry in Antoing, Belgium. Traditional starter solutions (DOL, star-delta, soft starters) have been known to generate high current peaks and thermal overloads (motor and transformer) that limit the number of start-ups per hour, and the adaptability to production needs, as well as quarter-hour peak problems.

The Danfoss solution is hoped, instead, to deliver 98% efficiency with no thermal overload.

After 35 years of service, the grinder at the Sagrex quarry was experiencing performance issues, such as untimely shutdowns caused by the accidental introduction of uncrushable parts. The VLT® AutomationDrive FC 302 is a vector frequency converter that limits the starting current to a minimum, while continuously monitoring the motor torque. The high-speed control card combined with the speed measurement of an encoder placed on the motor, makes it possible to immediately stop the machine as soon as the reference torque threshold is exceeded. When the torque is controlled, the risk of damage to the machine is also under control. The machine is furthermore said to be able to start up as often as desired, without disturbing other connections to the same transformer.

To maintain an acceptable temperature in the technical room without the use of a chiller, the AC drive cools air intake directly from the outdoor environment and rejects the hot air in the same way. This is the back-channel cooling solution, enabling 90% of heat produced to bypass the technical room. The room is protected from dust without the need for a condensing unit. 

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