rm core inductors - grounding/shielding?

[Krcwell]

Hi all,

I've been messing around with winding rm8 core inductors for some eq projects. It's been a pretty simple process as far as making them goes, but I'm trying to understand proper grounding/shielding of rm core inductors and if it's necessary.

Datasheets for the epcos cores I have seem to assume that the pins on the clamps used to hold the whole assembly together (wound bobbin, rm8 core halves) are grounded.

What is the purpose of grounding these pins?

I don't know much past how to calculate # of turns and assemble them. Please, educate me about proper implementation.

Much appreciated!

Keith

 

[trobbins]

The ferrite has some resistivity.  The clamps serve the dual purpose of providing a grounding mechanism, so that the core isn't floating (which may be hazardous, or require additional insulation to achieve a compliance requirement).

The core does provide electromagnetic screening - that's its job, but of course the core is not all encompassing.  Similarly with the grounded core providing electrostatic screening.

Stray flux is best managed by using a manufacturer gapped core (ground centre leg with defined AL value)), rather than you padding out a spacing between core halves.

Achieving a high Q may partly be affected by padding the winding so it is as far from any machined gap as possible.

Screening the hole part and wiring is up to you.