Page 1 of 1

Minimum current through psu choke to reach nominal H?

PostPosted: Wed Dec 25, 2013 7:05 pm
by MaciekP
Hello,
Do you know what is a minimum mA current you have to run through lundahl choke like LL1673 20H max 100mA to have the nominal 20H inductance? Is any rule? Is it 30, 40% of nominal current?

Re: Minimum current through psu choke to reach nominal H?

PostPosted: Thu Dec 26, 2013 10:49 am
by MaciekP
Btw, this is not a choke input question setup and minimum current to make it working, but rather choke only charakteristics and usable current range. At one end we have the max core tesla limitation for a particular core gap to handle DC current, at the other end we have a minimum current to enable the inductance generation

Re: Minimum current through psu choke to reach nominal H?

PostPosted: Tue Apr 07, 2015 8:00 am
by J. Leven
perhaps you should ask Per Lundahl

Re: Minimum current through psu choke to reach nominal H?

PostPosted: Sun Feb 28, 2016 11:01 pm
by Jac19
Sorry Maciek, I do not have very much time to check the forum often.

If you ask me, there is no minimum current, as long as you take a few mA.

Only when you measure it with an inductance meter, the core is struggling against the reversal of the magnetic direction all of the time, and it's a big piece of iron. So then a 20H choke appears may be 8...10H only, but that is because of iron loss in this micro signal range. Specially when tested at 1kHz. However ar 50Hz and DC current, this effect is gone, and you get a nice 20H.

Re: Minimum current through psu choke to reach nominal H?

PostPosted: Wed Sep 13, 2017 2:46 pm
by RhythMick
I believe the quick "rule of thumb" for LC filter is

Critical Choke Current = Voltage / Inductance

So for example with a transformer secondary of 400-0-400 and a tube rectifier drop of 50V, the first choke sees 350v. If it is (say) 20H, then you must ensure that at least 17.5mA flows to avoid the voltage rising.