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Motor-bearing currents
EMC noise in drive units

Drive units evolved with efficient frequency converts (FC), advanced power electronics and control engineering to a complex system. The possibility to switch within a few µs high voltages gains to more efficient FCs, but also lead to higher electromagnetic noise. Even with consistent PCB-layouts and good synchronization of hard- and software there is a need of additionally EMC actions to be done. Usually there will be mains filter to suppress the noise towards grid and stay within the given limits. In terms of EMC topics towards generator/motor often only shielded cables are used, which are protecting other devices for radiated emissions. Anyway, they do not shield the generator/motor itself for conducted emissions, so the high frequency common-mode-currents are flowing unresisted to the generator/motor. The capacitance of the motor bearings has a low impedance at such high frequencies and so motor bearing current occurs., which can lead even to mechanically destruction of the bearings. Even if the destruction is not happening directly the additional CM-currents are heating up the system and especially the grease, which leads to an accelerated aging and higher maintenance expenses.

CoolBlue and NaLA have proven in many applications that their good absorption and easy installation is an effective, cheap and maintenance-free solution. It is our pleasure to support you with measurements on site and helping to reduce the EMC-noise within your system.

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