The right rotation for EMC testing

From hearing aids to commercial aircraft: electromagnetic compatibility is important wherever electrical currents flow. Both the emitted interference from the device and its immunity to external interference from electromagnetic fields are tested.
Larger test laboratories, for example for cars, such as those realised by Frankonia, are often equipped with a turntable. This was also the case in a project for a Chinese customer in which such an electromagnetic compatibility test laboratory was developed. The turntable here has a diameter of seven metres and can accommodate test specimens weighing up to 20 tonnes. During a test cycle, which usually lasts several hours, it performs a rotation of 400 degrees and is designed for a load of 20 tonnes. 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 during the tests - 10 kV voltage at 700 A to be precise. The design engineers were therefore faced with the challenge of feeding several cables with a considerable cross section and weight through the turntable. Furthermore, all components had to be completely neutral as far as electromagnetic waves were concerned.

How do you solve this problem? The answer is, in a nutshell: With an energy chain from igus® and a corresponding rotation module.
To be more precise, the rotation module consists of an energy chain in "reverse bend radius" design, i.e. with a reverse bend radius. The chain is tilted 90 degrees to the usual installation method, i.e. it is positioned on edge and guided in a specially developed trough. The result is a compact and extremely robust cable carrier system for rotating movements. Specifically, ESD-compliant chains from the E4 programme were used here, which differ from conventional materials due to the addition of graphite 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 side-by-side chain runs touch each other or come into contact with the trough. This would influence the electromagnetic compatibility test result. As the rotation module has an outer diameter of almost six metres, the energy chain must also be guided safely and with little friction. So-called "floating islands" are therefore used as special guide elements that also reduce noise. Finally, centre stays in the chain ensure optimum guidance of the six chainflex® cables, which have been specially developed for moving applications.

Frankonia has already gained extensive experience with the igus® rotary modules. Andreas Heindl: "When we design electromagnetic compatibility test halls with turntables, the modules are simply the best solution. We can't use alternatives such as slip rings for electromagnetic compatibility tests because the cable and guidance must not cause any interference that could influence the measurement result." For these reasons, great importance is also attached to very good shielding of the cables, and special connecting elements are used for the connections. Finally, the electromagnetic compatibility test facility with the "XXL" rotation module, the ESD-energy chain and the 10 kV chainflex® cable was assembled in China - by Frankonia personnel on site and with the support of igus® fitters in China.