The right rotation for EMC testing

Profile

• What was needed: ESD-compatible energy chain from the E4 product range in reverse bending radius design, "floating islands" as guide elements, chainflex cables
• Requirements: Safe routing of some cables with a particularly large cross section, exclusively neutral components with regard to electromagnetic waves
• Industry: Test laboratory
• Success for the customer: Flexible chain solution that moves with the rotation, neutral solution that does not falsify the measurement results in the test laboratory, support during installation at the end customer

Problem

From hearing aids to commercial aircraft: Electromagnetic compatibility, or EMC for short, is important wherever electrical currents flow. Both the interference emitted from the device and its insensitivity to external interference from electromagnetic fields are tested.
Larger test laboratories, e.g. for cars, such as those implemented by Frankonia, are often equipped with a rotary table.  This is also the case in a project for a Chinese customer where such an electromagnetic compatibility test laboratory was developed. The rotary table here has a diameter of seven metres and can accommodate heavy test objects weighing up to 20 tons. During a test cycle, which usually lasts several hours, it rotates 400 degrees and is  designed for a load of 20 tons. It has connections for generators, transformers and electric motors.  One of the special features of the project was that the components had to be supplied with medium voltage - more precisely: 10kV voltage at 700A - during the tests. The designers were faced with the challenge of guiding several cables with considerable cross sections and weights through the rotary table. Furthermore, all components must be completely neutral in terms of electromagnetic waves.

Solution

How do you solve this problem? The answer is, in a nutshell: With energy chains from igus and an associated rotation module.
More precisely, the rotation module consists of an energy chain in Reverse Bend Radius design. The chain is tilted by 90 degrees to the usual installation type, i.e. placed on edge, so to speak, and guided in a specially developed trough. The result is a compact and extremely robust energy supply system for rotating movements.  Specifically, ESD-compatible chains from the E4 product range were used here, which differ from conventional materials by a graphite admixture for explosion risk areas. Unlike conventional energy chains, these are neutral as far as electromagnetic waves are concerned. Static charges can otherwise occur if the adjacent chain runs touch each other or come into contact with the trough.  This would influence the electromagnetic compatibility test result.  Since the rotary module has an outer diameter of almost six metres, the energy chain must also be guided safely and with low friction. So-called "floating islands" are therefore used as special guide elements, which at the same time reduce noise generation. Finally, middle links in the chain ensure optimum guidance of the six chainflex cables, which were specifically developed for moving applications.

Assembly in China with support from igus

Frankonia has already gained extensive experience with the igus rotary modules. Andreas Heindl: "When we plan electromagnetic compatibility test halls with rotary discs, the modules are simply the best solution. We cannot use alternatives such as slip rings for electromagnetic compatibility tests, because no interference that could influence the measurement result is allowed to come from the cables and guides." For these reasons, great importance is also attached to a very good shielding of the cables, and special joining links are used for the connections. Most recently, the electromagnetic compatibility test facility was installed in China with the "XXL" rotary module, the ESD energy chain and the 10 kV chainflex cables by Frankonia personnel on site and with the support of igus fitters in China.