# flyback leakage inductance

Discussion in 'General Electronics Chat' started by jagadeeshj, May 6, 2013.

1. ### jagadeeshj Thread Starter New Member

Jan 7, 2013
3
0
Flyback transformer Turns canculation and gap length
I read about designing flyback transformer desing from abraham pressman book I have ungapped ferrite core how can i get the required primary inductance. someone tell me how can i determine the gap length and number of turns.​

2. ### jagadeeshj Thread Starter New Member

Jan 7, 2013
3
0
Hello i wound a flyback transformer by hand and i calculated the leakage inductance by shorting secondary windings. the problem is i measure half of the primary inductance as leakage inductance i.e my Lp is 5.6mH and Leakage inductance is 2.3mH. how can i overcome this problem. I have to hand wind my transformer as i have no other go... pls suggest me some tips to reduce my leakage inductance.......

Also pls tell me does this problem reduces the output efficiency......

3. ### jagadeeshj Thread Starter New Member

Jan 7, 2013
3
0
Hello i wound a flyback transformer by hand and i calculated the leakage inductance by shorting secondary windings. the problem is i measure half of the primary inductance as leakage inductance i.e my Lp is 5.6mH and Leakage inductance is 2.3mH. how can i overcome this problem. I have to hand wind my transformer as i have no other go... pls suggest me some tips to reduce my leakage inductance.......

Also pls tell me does this problem reduces the output efficiency......

4. ### Wendy Moderator

Mar 24, 2008
20,772
2,540
One thread is enough, lets keep it over here.

5. ### crutschow Expert

Mar 14, 2008
13,520
3,386
You can reduce leakage inductance by uniformly winding the secondary windings over the primary windings or by winding the primary and secondary in bifilar fashion. The leakage inductance in a properly made transformer should normally be no more than about 5% of the primary inductance. What is the shape of the core?

Yes, the leakage inductance will reduce efficiency since it generates a voltage spike on the primary which has an energy of 1/2 LI^2 where L is the leakage inductance and I is the maximum ON current. This energy must be dissipated.