Is it good or even used practice to filter out common-mode EMI in 3-phase industrial inverter (IGBT) phase outputs using phase-to-earth Y-capacitors? High du/dt might limit the lifetime of such capacitor, can ceramic y-capacitors handle this if film capacitors are in problems? 1000-3000V/us was mentioned in film capacitor's datasheet of for example TDK B81123. Any reason to use the caps in the phase outputs from the IGBT protection point of view (suppress voltage spikes or ESD)?

Wasn't able to find any literature related to the issue. Also DC-link could be tied to earth using Y-caps, not much of that either.

  • \$\begingroup\$ Do you have a 3ph CM choke? what power levels? Ceramic is not recommended if film is a problem. How much energy is being absorbed in each pulse and what rate? (P_rms or I_rms)? Consider a snubber to dump energy in RC \$\endgroup\$ Feb 14 '18 at 19:49
  • \$\begingroup\$ The backstory is that I'm designing 3-phase inverter based on IGBT-module. Target is to achieve robust PCB-level design for harsh industrial environments fulfilling CE-marking requirements regarding EMI and also from the other aspect protecting the sensitive IGBT-module from ESD/reflected wave overvoltages. Being PCB-level design, no chokes or inductors, additional filtering can be put later on between load and inverter. Was thinking about MOV in the outputs, but that's not propably good idea at all, so next was idea about Y-caps. DC-link is boost PFC from 230VAC supply -> 400VDC. \$\endgroup\$
    – thobie
    Feb 14 '18 at 21:20

It is an option to put such caps at the inverter output to guide the common mode current to ground before it would go mainly over the motor bearings to ground (which is often a major lifetime issue for variable speed controlled drives).


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