Re: B-H curves
Patrick, Wed Feb 06 2019, 06:54AM


Perhaps this :

Re: B-H curves
Sulaiman, Wed Feb 06 2019, 10:46AM

or this ?

H is represented simply by current
B is more difficult as it is represented by integral(voltage)
also, your test equipment has to be able to supply enough current to saturate the material,
for a closed loop with no airgap(s) usually not too difficult,
if there is an airgap then high current may be required.

Re: B-H curves
Hazmatt_(The Underdog), Sat Feb 09 2019, 03:29AM

I like that circuit Sulaiman posted, but the ramp generator will not work.
There is no signal feeding the current amplifier, so you will not get any drive signal.
I suspect the author meant to setup the PA as a class B amplifier with the 51 ohm resistors feeding 1N914 diodes, or some such arrangement for the final PA.

But as it stands, the ramp generator has a typo.

Re: B-H curves
Patrick, Sat Feb 09 2019, 05:13AM

what i only need to know saturation current. like A-t, know the amps the number of turns and then the duration of each pulse. then every 3 seconds pulse 3 amps through 10 turns for 1mS and keep increasing the mS duration until the current isnt held back at all.

i guess i dont need the B-H graph just a saturation like plot on a scope.

Re: B-H curves
Paul Benham, Wed Mar 06 2019, 07:45PM

If you know the core material, could you not just calculate it?

I guess if it is an EI core it is more difficult.

If you put it in your circuit and add a small seriies resistor you could scope the current and see if anything nasty is happening?

Paul

Re: B-H curves
2Spoons, Wed Mar 06 2019, 09:08PM


Actually there is : its being driven by monitoring the supply current of the opamps. Which seems a weird way to do it.

If all you want is Isat, apply a constant voltage and look for the knee in the current ramp.

Re: B-H curves
johnf, Thu Mar 07 2019, 06:58AM

Core saturation is easy to measure
pulse generator feeding a large fet, drain has inductor to +Vcc, source earthed through 0.1ohm resistor. Scope earth and drain for inductor volts scope channel 2 across the source resistor now you have saturation point vs current
what more do you need to know

oh number of turns of course then you get an idea of bMax
watch slope with scope trigger set when voltage suddenly gets kink going more vertical you have found saturation point