2017 Technical Webinar
Challenged by EMC Compliance?
Overview:
Exploring the use of filters on various applications, installations and designs. This will include a review of how filter components react at different frequencies.
- Overview of EMC
- What is it?
- Challenges
- Components at high frequencies
- How to choose a line filter
- Insertion loss
- Common Mode / Differential Mode
- Parameters
- High pot, Insulation resistance, voltage, current, temperature
- Grounding and Cable layout
- Coupling Mechanisms
- Good/Bad examples of different configurations
- Examples of how different filters react in similar configurations
Who Should Attend?:
Engineers challenged by EMC compliance. (R&D, Compliance, Design, Electrical, Mechanical)
David Armitage
David Armitage is the Manager of Engineering for Schaffner EMC and has worked in the EMC industry for over 20 years. In his current role he manages the engineering, design, quality and technical efforts for North and South America. David has also worked for an EMC compliance test house where he evaluated products to ensure they met the various FCC, CE and Mil standards. He has served as the Expert for Interference Technology’s “Ask the Expert” EMI filtering forum and Co-Authored an article for EC&M magazine. He has a BSEE from Wilkes University, an MBA from Pepperdine University and is a PMI credentialed Project Management Professional.
Q&A
The following questions were asked during the live presentation. Click each question to view its answer.
Is it ever a good idea to design small filter capacitors (e.g. C0G, 100pF) on the inputs or the output of an opamp to circuit common? If so, when?
Yes, you can create an LC or RC filter. I would recommend using an even smaller C (10-33pF). You do not want to degrade the stability.
How to evalute filter from manufacturer A or B?
You can first look at the insertion loss curves to see how similar they are at 50 ohms. Then I would check the individual inductance and capacitance values. Ideally you want to match the individual values not just the filters total values. You can then review the mechanicals of the filter. Physical testing of the two filters is the ultimate comparison.
"A shield is not a shield unless it is terminated/grounded" Is this saying that a shield must be "grounded" in order to work? How about a shield on a satellite in orbit? Not grounded. Proper termination is key, grounding isn't critical.
You are correct, termination is a better description for such an installation.
IEC 61000-4-6 requires conducted immunity from 150 kHz to 80MHz
Correct, and the filters can help in complying with this immunity standard. The presentation focused more on Emission standards, but some filters are designed to extend their attenuation range above 30MHz to 200MHz and higher.
Why do conducted emissions turn into radiated emissions at 30 MHz?
A field will be created above and below 30MHz and could be measured with the correct type of antenna. The standards use 30MHz as a breaking point due to wavelength and how the emissions will propagate most effectively away from their source. Under 30MHz the noise is typically restricted to traveling on cables. The emission path back to the power connection is of concern. Above 30MHz the noise is more likely to radiate and to capture the overall emission level of a device under test an antenna is used.
Could dangerous voltage be present on the filter case with an improperly grounded filter?
There are many different designs of EMC filters and to effectively answer this question it would be better to focus on a specific example. That being said for an EMC filter with a small capacitance value to ground, if it is not in a fault condition the case or housing should be safe. As the capacitance value from phase to earth increases a larger amount of leakage current will pass to the housing. In addition the filters carry various safety agency approvals to ensure safe operation.