A fully natural product, beet sugar is perfect for those who are looking for natural sweeteners. Sugar beets count amongst the few plants that can store their energy directly in the form of sugar. This sugar is then extracted from the beets at sugar factories, where it is separated from other substances and crystallized. Nordzucker AG from Braunschweig (Lower Saxony) is one of the leading manufacturers of sugar in Europe. Nordzucker’s largest production site is in Uelzen, which is also one of the most advanced sites in Europe.
Sugar centrifuges play a key role in the process of making sugar: they separate crystalline sugar from a sticky syrup. The Uelzen sugar factory houses almost three dozen centrifuges. In one of the four centrifuge stations, white sugar station 2, the BMA B1750 batch centrifuges are controlled by ABB’s regenerative industrial drives, with the latest ACS880-17 systems set up on three of these. The M3BP series 8-pole IE2 process motors of the centrifuges are also made by ABB. The centrifuges and the drive solution were supplied by BMA Braunschweigische Maschinenbauanstalt AG, which specializes in systems for industrial production and sugar refining.
Challenging operating conditions
During the operation of centrifuges, their regenerative drives and electric motors must work under extreme loads. The motor must accelerate the batch at the maximum speed of 1000 rpm, and at full torque, for about 15 to 20 seconds, so that the syrup separates from the sugar crystals purifying them in the centrifuge. Then, the motor slows the centrifuge down as quickly as possible.
The regenerative drive must be able to speed up and slow down quickly without overheating. This is not a typical kind of load for the motor either. And both must work together without any problems. Another challenge is the heat in the factory during the beet campaign. Regenerative drives and motors are under significantly heavier loads than normal during this period.
Recovering braking energy
The ACS880-17 cabinet-built regenerative drives are adjusted for the 250 kW motors of the centrifuges. The regenerative capability makes it possible to direct the braking energy of the motors to the drive, and then to feed it back into the grid. Compared to other braking methods, such as mechanical braking and resistance braking, the ACS880-17 drive saves significantly more energy. The regenerative function is necessary to enable electric braking. Otherwise, large braking resistors would be needed that release all the energy converting it into heat. Cooling them down would require additional cooling systems.
Comprehensive safety functions
ACS880-17 meets the strict occupational safety requirements set by the Employer Liability Insurance Association for the operation of sugar centrifuges. The industrial drive has the safe torque off (STO) safety feature in its standard configuration. However, for applications with big sugar centrifuges, this protection is not sufficient. The optional FSO-12 safety module expands the safety functions of the regenerative drive at the Uelzen factory. This auxiliary component is integrated into the regenerative drive. Typical safety functions, such as Safe Stop 1 (SS1), Safe Brake Control (SBC) and Safely-Limited Speed (SLS), are implemented in this compact module.
The ACS880-17 drives were able to demonstrate their reliability during the demanding seasonal operation. The ABB´s regenerative drives are also appreciated, as they are easy to operate. Everything is provided in clear language in the control panel menu.