Electronics > Beginners
Ferrite core saturation
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strawberry:
how to measure saturation current and convert in Teslas and vise versa?
jmelson:
You have to know all the mechanical features of the inductor.  So:
number of turns
permeability of core material
surface area the gap of any air gap
cross sectional area of core

Given this, you can calculate the average flux in the core for any current.  Then, given the saturation flux, you can see where this intersects the current.

Jon
jmelson:
Oh, the other way.  Apply a constant voltage to the inductor with a transistor that turns on and off, and measure current with a series resistor.  Observe voltage across resistor with an oscilloscope.  You will get an approximately linear current ramp up to some point, then the current will start to rise faster.  Roughly where the linear curves up is the point you can call saturation.

Jon
T3sl4co1l:
You don't directly convert amperes to tesla.

Instead, apply a pulse waveform, and measure the area of the pulse, from zero to the point of saturation.  If a square pulse is used, the area is simply V(on) * t(on).

tesla == V.s/m^2 == V.us / (mm)^2.  Once you know the cross sectional area of the core (don't forget to divide V.s by number of turns), you have tesla.

It's not very important though, as ferrites all saturate in the 0.2-0.4T range, and core loss typically limits operation to a fraction of that.

Tim
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