# Inductor calculation help

Discussion in 'General Electronics Chat' started by mat350z1, Dec 10, 2014.

1. ### mat350z1 Thread Starter New Member

Dec 4, 2014
7
1
So Im trying to figure out the inductance of the primary of my flyback transformer so that i can calculate its current draw at certain frequencies. Im having trouble doing this. i seem to always get values that are way off the charts when it comes to inductance. does anyone know how to figure out the inductance of this coil on the flyback. there are seven turns of solid wire on the ferrite core which is about 1.1cm by 1.5cm. (its not round its a square core) length of the coil is about 2.5 cm. does anyone know what the inductance of this coil could be. with out measuring it??. I have attached a picture.

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
784
Sure - post the picture. It may help.

3. ### mat350z1 Thread Starter New Member

Dec 4, 2014
7
1
whoops here it is

4. ### Midnite Jim New Member

Dec 10, 2014
2
0
You can't calculate it unless you know the Al parameter of the core material. If you have the Al for the material then L= Al *turns^2 (usually in nanohenrys). Otherwise you can measure it with a dual channel scope using the relationship, V=L*di/dt. V is the voltage across the coil and the other channel is the current through the coil, (voltage measured across a small resistor inseries with the coil), which will be a linear ramp increasing in time. From the slope of the "current" you can get the amps per second increase, which is your di/dt then just solve for L.