Re: EMI CHOKE QUESTION

"Yzordderrex" <yzordderrex@xxxxxxxxxxx> wrote in message
news:1116506033.265934.149800@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
> I have recently been given responsibility for EMI choke design. The
> company I work for makes motor controls.
>
> I am looking at a 12amp servo drive (single phase 230v input) that will
> pull about 150 amps peak on the input side when balls to the walls 300%
> output.
>
> The EMI filter choke is wound like any other single phase unit you
> would see on a toroid. Winding A on one side, and winding B on the
> other side of the ring. Each winding taking up about 160 degrees of
> ring so that there is some voltage creepage distance.
>
> I have wound a 10 turn tertiary winding on the core that I use to
> measure inductance. I jam my 30v bench supply into the tertiary
> winding an watch the rate of rise of current to measure the inductance.
>
> When I excite the core with 150 amps not all of the flux is cancelled
> so that the inductance goes to nearly zero. I'm assuming that the
> filter is probably useless at the peaks of the line currents.
>
> Would I be better off using an insulated wire and wind each coil say
> 330 degrees and interleave the coils - bifilar?
>
> We have gear to measure and I will probably proceed on this path for
> today. Just soliciting your thoughts.

dont forget that although the flux on each side of the toroid cancel
eachother out so there is no circular flow around the core, they do however
add up to cuase a net flux across the core, wich if high enough wil cuase
enough flow through the air to saturate the whole core.

Colin =^.^=


.

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