Passing EMC Testing Without Redesign: Line Filters Make It Possible

Horror scenario in an EMC test situation: the design does not meet the specified guidelines, and a filter solution must be installed as quickly as possible. This is usually not possible without a partial redesign, especially for small applications. Not only does this cost precious time, it can be very expensive.

A line filter can help here: the ready-to-use component already contains a common mode choke and capacitors in a compact design, which can be quickly mounted through faston connectors. They are used for attenuation of common-mode and differential-mode interference over a wide frequency range.

High quality line filters like the WE-CLFS line filters are compact and easy-to-use filter solutions.

There are several important applications for the WE-CLFS line filters, including:

  • Industrial electronics
  • Switch mode power supplies (SMPS)
  • Telecommunication devices
  • Household appliances (white goods)

Special Features of WE-CLFS Line Filters

What makes WE-CLFS superior to other EMC line filters? Here are a few of the key benefits:

  • Insertion loss measurement according to standard
  • Wide frequency measuring range
  • Good characteristics for temperature, DC bias, and aging
  • VDE and UL certification
  • Easy and fast assembly through faston connectors
  • Noise suppression in common and differential mode
  • The first LTspice models made of S-parameter

Available in 3 Convenient Sizes

WE-CLFS line filters come in three convenient sizes for your design:

  • Single stage: Very compact design
  • Single stage advanced: Improved differential mode noise attenuation
  • Two stage: Extreme differential and common mode noise attenuation

Well Prepared for the EMC test

Wurth Electronics is the first to provide this new LTspice model made of real S-parameter data, with which you can quickly and easily simulate and find out whether the filter is suitable for your application or not.

In case you want to establish a cable connection, a variable ground connection is also integrated, as well as a DC point, with which you can simulate also low frequencies. You can download LTspice model and the S-parameter data here on the website.

Easy Simulation with the REDEXPERT Simulator!

Want to try our WE-CLFS line filters, but don’t want to commit to purchasing? You can simulate them for free using our REDEXPERT tool!

If you are looking for a simple, quick way to pass your EMC test without redesigning your PCB, try our WE-CLFS line filters and order samples today and get WE-CLFS delivered within 24 or 48 hours!

this very nice post it is useful tips and idea for post. best information for blog. thank for sharing us....

- Amit

When already dielectric Al2O3 exists on the anode, why do we need a paper separator? cant Al2O3 provide required insulation and prevent shorting anode with cathode foil?


Hi Pradikrc,

The separator is both, a physical separation between anode and cathode foil and more than that the carrier of the electrolyte. Over the time the dry out phenomenon will happen to an electrolyte capacitor. The separator contains additional electrolyte to keep the capacitor in operation.

More than that, for special electrolytic capacitors e.g. audio or flash light the separator has additional functions or at least influences the capacitor’s performance.

-Würth Elektronik

When anode is just an Al foil why cant we use just an Al foil for cathode as well, why is there an extra electrolyte for the cathode?


Hi Pradikrc,

Both, the anode and the cathode foil are basically Aluminum foil. The anode foil is much more complex. Two production steps, first etching creates a highly roughened surface, while the second step - forming - creates the necessary oxide layer.

The cathode foil is normally just an aluminum foil without any treatment. The electrolyte is a liquid that is necessary to contact all the surface area of the anode foil and activate the maximum capacitance of the capacitor.

Without the electrolyte the capacitor cannot store the energy, the over-the-time dry out phenomenon will show the reduced capacitance - means, only a reduced area of the anode foil will work properly

-Würth Elektronik

Q. What causes in reality for the Al electrolyte capacitor to breakdown or explode when it was subject to reverse voltage?


Hi Pradikrc,

In regular conditions there is the Anode foil with a certain thickness of the dielectric Aluminum oxide layer on its surface. The voltage applied in the correct direction will maintain the thickness of the oxide layer. In operation the voltage reduction from Anode to Cathode foil will happen in the oxide layer.

Reverse voltage will reduce the oxide layer immediately. Without the oxide layer the applied voltage will cause shortage, the high current starts heating up the electrolyte rapidly, boiling – generating gas – which finally causes the overpressure and explosion of the capacitor.

-Würth Elektronik

When removed anode foil from the Al electrolyte capacitor was tested multiple times it showed short circuit from one point of the foil to another point of the anode foil, in reality it shouldn't because it has oxide layer, what made it to short?


Informative, thanks.


Good article...need to read further