Powerful Knowledge 18 - EMI in power electronics

High speed switching in power electronic systems has the potential to create electromagnetic interference (EMI). Emissions can be conducted out through cables or radiated out as an RF emission.
In this episode, number 18 of our 'Powerful Knowledge' series, we discuss the source of some of these emissions, how they are coupled to the outside world and how they can be mitigated.
There are some great practical tips on debugging EMI in this video!
#powerelectronics #stemeducation #knowledgeispower #rfi

[@sagarnikam407]

Thank you for sharing the brief insight

[@Janamejaya.Channegowda]

Thank you for sharing, really useful content, keep up the great work.

[@neethus3294]

Hello, Very nice presentation! Could you please make a video on active inrush limiters using p type mosfets when there are bulk capacitors in DC-DC Converters? It would be helpful. Thank you.

[@cnchow323]

I enjoy this webinar. it is extremely useful from engineering view point. Can you do another webinar on actual high power for example 2-3KW output convertor

[@ElectronicmindsUK]

Thanks for your feedback and good to hear that this was useful for you. We are working on a different set of videos now but will put your request onto our list for future ideas. Many thanks!

[@sowmyaakella9168]

What is a good starting value to put in the first pass design for a CM choke,(for say filtering higher frequency >2MHz) , is there a rule of thumb value ? Another unrelated question - I have seen CM chokes connected to the two ends of a shunt resistor, in a design where the shunt resistor sits on one PCB and the voltage across the shunt connects to another PCB via cables (and is eventually connected to say an ADC)?

[@ElectronicmindsUK]

The value of CM Choke will depend on many aspects of the design and it is hard to give accurate guidance on this. However, as a good starting point, for offline isolated supplies up to about 100W, typical values are around 10mH. Start with that and then test/iterate. Remember that the CM choke (and any inductor) is only inductive over a specific range of operating frequencies. For your example of the CM Choke on a shunt resistor, this maybe to attenuate CM noise from the power stage (shunt) reaching the control board. CM noise is an interesting thing. It will find its way through all the parasitic elements of your design (i.e. the bits which you might not know are there) and it is key to understand the dominant coupling paths.

[@joskom6267]

Hi, thank you for the presentation. Relay awesome content. I have a crazy question: from safety perspective it is not recommended, but if we want to see quickly only DM mode noise in the emi signature up to 2 MHz , should we see it if we disconnect PE wire between DUT and LISN?

[@ElectronicmindsUK]

Glad to hear that you liked the content! If you remove the PE wire then the common-mode noise will find it harder in the lower frequency ranges to find its way to the LISN. However, there are lots of other parasitic paths, mainly capacitive which will allow common-mode current to find its way back to the LISN and get registered. So removing the PE wire will most likely reduce the levels you see but the spectrum will still contain CM noise. You can achieve a better result using splitters to isolate DM and CM noise, check out this link www.analog.com/en/analog-dialogue/articles/separating-common-mode-and-differential-mode-emissions-in-conducted-emissions-testing.html