# Need help on finding out current comsumed by Inductance!!!

#### bmxerds

Joined Sep 4, 2012
16
Hello everybody I need some information on how to find out how much amps a toroid I want to wind will comsume. Basically I want to wind the primary on a toroid and I already know how to get the right uh, but I don't know how much uh I need.
My circuit is going to have an out put of 12-14vdc pulsed at 10-50khz
I want the current draw to be about 5 amps
I just need to know how much current the inductance of my toroid is going to comsume
The toroid is rated above 5 amp

#### wayneh

Joined Sep 9, 2010
17,476
It's complicated. The draw on the primary will depend on the load on the secondary, and the degree of magnetic coupling in between, which in turn depends on the permeability of the toroid material. Are you asking about the losses into the toroid itself?

At low frequency, the DC resistance of the windings can dominate, but at higher frequencies, the coil inductance-times-frequency will provide the majority of the overall impedance and DC resistance will be insignificant.

#### Dodgydave

Joined Jun 22, 2012
11,151
You need to know its Inductance (L) in Henries ,then you can calculate its Reactance ( XL) at the Frequencies (F) your using.

XL= 6.284 xFxL

#### bmxerds

Joined Sep 4, 2012
16
Thank you very much!!! Reactance is the things I was looking for!!

#### crutschow

Joined Mar 14, 2008
33,370
An inductor doesn't "consume" current, it carries it.

If you are pulsing the inductor, then the equation you want is V = L di/dt or di = V/L dt where V is the voltage across the inductor, L is the inductance, dt is the time the voltage is applied, and di is the change in inductor current over the interval dt.

#### ErnieM

Joined Apr 24, 2011
8,363
I would need some sort of rough sketch to comment. The sketch can just show the input, output, where this inductor is, and where the switching element sits.

The inductance can easily be solved for in the time domain (L = V delta t / delta i) once you can see the voltages across it for the on and off times. Right now I can't see them without a sketch.