Hi
I am working on a high power frequency inverter (>1kW) and have a "funny" looking emission graph
The converter is the typical inverter type, EMC filter->3 Phase Rectifier->DC Inductor->DC Link capacitor->6 switch Inverter->Motor
Like this:
We stripped down the circuits and isolated the noise to the EMC filter and bridge rectifier.
The problem is the very high conducted emission noise at 150kHz:
(Conducted emission plot narrowed in from 150kHz to 2MHz, conducted with a 2-stage EMC filter and a bridge rectifier with a capacitor on the output and a resistive load)
The bridge rectifier is a part of an intregrated power module, but that noise also comes from a standard single phase rectifier
First thought would be that the noise is coming from the reverse recovery of the diodes, but the noise increases a less load (< 200W), and I would think the reverse recovery current glitch would be worse at higher currents running in the bridge rectifier
I have tried with snubbers and that did not help.
Any insights into the cause and the remedy?
Thanks
Klaus