Building Schaffner FN410 Line Filter - Inductors Connected to Ground

[Kilamir]

I am trying to build the Schaffner line filter FN410 out of discrete parts. The datasheet for that part can be seen here:

http://www.schaffner.com/corporate/en/register_log.asp?language_id=12&fN=http%3A%2F%2Fwww%2Eschaffner%2Ecom%2Fcomponents%2Fen%2F%5Fpdf%2FDatasheet+FN410+e+6%2Epdf

Anyways, they list all the values for the inductors and capacitors that they use in the circuit except for the inductors connected to ground. I believe they help against incoming common-mode noise. Does anybody have an idea what inductance should be use for those inductors?

Thanks in advance!

 

[berkeman]

I am trying to build the Schaffner line filter FN410 out of discrete parts. The datasheet for that part can be seen here:

http://www.schaffner.com/corporate/en/register_log.asp?language_id=12&fN=http%3A%2F%2Fwww%2Eschaffner%2Ecom%2Fcomponents%2Fen%2F%5Fpdf%2FDatasheet+FN410+e+6%2Epdf

Anyways, they list all the values for the inductors and capacitors that they use in the circuit except for the inductors connected to ground. I believe they help against incoming common-mode noise. Does anybody have an idea what inductance should be use for those inductors?

Thanks in advance!

Welcome to the PF, Kilamir. It's a great place.

I don't see any inductors to ground in the filter datasheet schematic, and inductors are not usually connected to ground in this type of filter anyway. In general, the topology will be some series high impedances (the inductors) and some parallel low impedances (the X and Y capacitors) to provide the lowpass filtering characteristics (for both common mode and differential mode).

In the schematic for this filter, there is an X cap for the differential lowpass filter characteristic (in conjunction with the inductors), and two Y caps for the common-mode lowpass filter characteristic. Of course, the Y caps also provide some additional differential LPF contribution as well (Quiz Question -- why?). Does that help?

 

[ravenprp]

First of all, great job on attempting to build the Schaffner FN410 line filter out of discrete parts. It definitely takes some skill and knowledge to do so. As for the inductors connected to ground, the datasheet does not specify the exact inductance values because it can vary depending on the specific application and environment. Generally, these inductors are used to suppress common-mode noise, so their value should be chosen based on the frequency range and amplitude of the noise you are trying to filter out. You can use a general rule of thumb of around 10-100 uH for these inductors, but it is always best to consult with a professional or perform some testing to determine the optimal value for your specific application. I hope this helps and good luck with your project!