Ferrite choke questions

[lynx]

Hi

i wanted to make a low pass filter to filter out noise from a power supply, initially my filter was working fine without getting hot,
but while i was connecting and disconnecting the low pass filter so i can test it's performance, my ferrite choke got hot and the
coil coating melted...

the ferrite choke was taken from an old device and probably it wasn't suitable for the current i wanted to pass ~2.5A, the wire
appeared to be less than 0.4mm.

now i did my own ferrite choke using 0.5mm tranformer wire on a Feroxcube TN19/11/10-3C90 ferrite bead the inductance is 23mH,
the capacitance of my filter is 4500uF and the corner frequency is 15Hz, i want to ask what value capacitor i should add so the surge
and spikes can be absorbed before the ferrite choke gets burned again?

thank you.

 

[dr pepper]

Sounds like the dc resistance is to high, have you measured it?, you can measure low resistances with a bench supply that has current limit.

 

[mvs sarma]

the chokes for filters in psu have to be got designed for the current that passes through it. neither the wire can be thinner , nor the ferrite selected should saturate.

 

[lynx]

for the burned inductor, i don't know the resistance, for the new one
it's less than half ohm, do you think i should try it as is? or is it going to get
burned too?

here's a datasheet for the core of my new inductor:

https://www.electro-tech-online.com/custompdfs/2013/08/tn191110.pdf

 

[dr pepper]

0.5 ohm @ 2.5 amps gives a drop of 1.25v which @ 2.5a is a (dc) disspation of 3.125 watts, for a small inductor this is a lot and it may well get hot.
Can you use thicker copper?

 

[lynx]

Hi

in fact the resistance it's just a few milliohms or less, my multimeter's probes
didn't do good contact

other than that..i tried the inductor i made and the filter works so great!! though
i would like it to do a bit more suppression, maybe i should build a Pi type?..

now about my hypothesis that i needed an extra capacitor maybe 100nF
to absorb the spikes so the inductor doesn't get burned...it was wrong?


THANKS!

 

[lynx]

any help??

 

[mvs sarma]

Don't bother,
the inductance is measured in milli/micro Henries and not in ohms. unless the coil is short, milli ohms should not be an issue to you. try using it in your application.

 

[lynx]

Don't bother,
the inductance is measured in milli/micro Henries and not in ohms

hi

yes that's right...who said differently?
dr pepper asked me how many ohms was my previous inductor, in case it was
decipating alot of power on it and as a result it was getting hot until it melted.


would you like to read again what i said at the post #6?,can somebody pls reply to
my questions at post #6? what i ask it is important to me, thank you.

 

[mvs sarma]

you can use pi filter
it can have electrolytic cap and ceramic disc cap in parallel, on either side of Inductor. the 100nF is not for inductor not to burn, but mainly to filter out higher frequency content of ripple or any possible spike.