Harmonics and Energy Reduced in High-Speed Centrifuge

Harmonics and Energy Cut in High-Speed Centrifuge

Challenge

  • Regenerative drive solution for high-speed centrifuge
  • Soft start to 10,000 RPM and controlled braking to standstill
  • Safety functions that take into account centrifugal forces amounting to 55000 times the gravity of the Earth
  • Control technology interaction between customer-specific, tailored systems and components

Solutions

  • PowerFlex® 755TR AC Drive – Regenerative Allen-Bradley PowerFlex® 755TR AC drive with harmonic mitigation
  • Invag AG – Commissioning and technical support provided by experienced system integrator, Invag AG, and Rockwell Automation

Results

  • Continuous product quality via optimized process and drive control system
  • Energy recovery back into the supply network
  • 20% energy savings during production
  • Reliable operation of lab equipment thanks to significant reduction of harmonic effects on the system current

Thanks to the modernization of the entire drive solution, spinning up the centrifuge has lost its impact on the power supply

Working for Iscador AGInvag AG was tasked with developing a drive solution for a high-speed centrifuge. These devices can only be found in two places worldwide: First, as part of an experimental research facility, and second, for the manufacturing of pharmaceuticals. In this instance, the entire component range, from the water-cooled motor, right up to the bearings, represented a special design for the production of the mistletoe drug, ISCADOR® of the anthroposophic medicine.

Iscador AG is a pharmaceutical company that supplies complementary medicine for integrative cancer treatment. In this context, the focus is on the healing power of the mistletoe within a holistic treatment concept. “The leaves, stems and berries of mistletoe are used for the production of our drug,” explains Dr. Gerhard Schaller, Head of Manufacturing and Member of the Executive Management at Iscador. “We harvest once in the cold and once in the warm season, as evergreens display seasonal variations with regard to the active substances. The lectine concentration is at its highest in winter, and the amount of viscotoxins increases in summer. We concentrate on a specific mix of both.”

Challenge

Mixing the two mistletoe extracts is still carried out on the basis of a process that can be traced back to Rudolf Steiner, the founder of Anthroposophy: The extract of mistletoe collected in winter is continuously dosed in the center of a rotating disk, which exhibits a raised lip at its edge, and moves outwards as a thin film towards the outer rim due to centrifugal force. The extract of summer mistletoe, on the other hand, is added drop by drop at certain positions from a height of one meter. Both types of extracts are then thoroughly mixed at the rim of the disk.

“The 1m-diameter titanium disk rotates at a speed of 10,000 RPM throughout the production process,” explains Christian Albisser, Head of Central Services at Iscador. “This results in a rim speed of 1,885 kph and centrifugal forces that are 55,000 times greater than the force of gravity.” This energy had to be mastered in terms of control technology.

In the past, this control has not been optimally achieved. The power supply was subjected to undesired feedback effects as soon as the facility entered the high-rpm-range. In some cases, certain consumers even had to be shut down in order to ensure network stability. With regard to lab equipment, having to sacrifice operating time is far from trivial.

Mixing the two mistletoe extracts is still carried out on the basis of a process that can be traced back to Rudolf Steiner, the founder of Anthroposophy.

“The facility is not continuously in operation. The summer and winter mistletoe extracts are only processed into a healing extract twice a year,” states Schaller, explaining why Iscador AG had been able to live with the previous solution despite these limitations. The modernization of the existing installation, which was scheduled for 2017, specified that the new driving force behind the rotating disc should not have an impact on the network and should also be regenerative to conserve the environment.

Additional challenges had to be tackled as well: The actual facility entirely consists of custom products, in some cases without corresponding data, and may not be modified. Furthermore, only a very small window was available for trial runs.

Solution

Discussing the task at hand with Rockwell Automation, it turned out quickly that the pharmaceutical company in Arlesheim was looking for the performance delivered by an Allen-Bradley® PowerFlex® 755TR AC drive.

“We had this extraordinary application with custom-designed motors that could under no circumstances be damaged,” explains Invag’s Executive Manager. “The immense centrifugal forces demanded appropriate safety precautions. Seven sub-processes had to function both in a combined manner and independently. The centrifuge had to start up softly, brake in a controlled fashion and allow for the recovery of braking energy without interference,” he summarizes.

At Iscador, the AC drive – specifically a 200 kW IP21 model – functions as the central motor element for the production of the mistletoe drug. The motor control system must harmonize with the oil lubrication system on the engine mounting as well as the cooling unit and the pressurized air, vacuum and helium supply of the facility. The AC drive must adapt the rotational speed in accordance with the amount of helium available to flood the disc area. “At Iscador, we had six minutes to spin up to 10,000 rpm. Then the titanium disk had to rotate at constant speed for three hours, with thermal generation and vibrations simultaneously kept within a very limited range,” describes Martin Neuenschwander, Commercial Engineer at Rockwell Automation.

Results

Simply “just” delivering, installing and powering up was definitely out of the question. Instead, the engineers from Invag and Rockwell Automation carefully approached the optimal parameter settings together with the customer on a step-by-step basis. The crux of the matter was understanding the peculiarities of the motor and its interaction with the AC drive. And all of this within a very limited window, as the next production phase was imminent.

“In Invag and Rockwell Automation, we have found two companies who can be characterized by their optimism and a willingness to press ahead even in difficult situations. Working together as a team, we ensured that we constantly moved forward,” says Albisser, explaining a cooperation that led to a tangible benefit for Iscador.

The PowerFlex 755TR mitigates the harmonics and therefore minimizes the voltage distortion of the supply network. Spinning up the centrifuge no longer has a detrimental effect on the work going on in the lab, because all other devices can now remain in operation during the production phase. The energy consumption is also lower.

“The power consumption during peak operation has been reduced by 22%. We now manufacture even more efficiently and without an impact on the rest of the building,” says Dr. Schaller, visibly happy with his department’s modernization project. “Invag and Rockwell Automation were really responsive. They not only wanted to understand the technical processes, but showed also interest in the concept of the anthroposophic treatment of cancer,” adds the Head of Iscador Manufacturing.

The results mentioned above are specific to Iscador AG and Invag AG’s use of Rockwell Automation products and services in conjunction with other products. Specific results may vary for other customers.

Allen-Bradley, PowerFlex and Rockwell Automation are trademarks of Rockwell Automation, Inc. Trademarks not belonging to Rockwell Automation are property of their respective companies.

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