I will here develop this tutorial for you learn how to use simple math to design a coil and predict its behavior under pulsed conditions.

First of all when working with a transformer core we than should try use the maximum of its ability.

the window is the first thing to think about.. the number of turns you can get into it will depend on the diameter of wire, the required isolation and coil former dimensions..

how to simplify and always get it work?

First calculate how much turns you can do for the core... for that we are goingto divide the core window area by 2 assuming we are able to use half of it with copper and the other half with space and insulation,... than divide this number by the diameter of the wire used squared since we are dealing with area... the result is the maximum number of turns you can do with this wire you have...

the isolation depends on the material you use but the bests are nomex... or poliimide films...

this films are required to isolate the coils layers at worst case condition...

here we find that the coil will occupy a maximum of space in the core...

the power a transformer can delivered is limited to the amount of copper you can wind on it...

the maximum voltage this transformer will be able to get out will depend on the primary turns and the power suppy voltage youhave

so for example we found that we can put 500turns plus the primary few turns in the core... how many turns can we use?

here you must calculate according to the core crossectional area, voltage, frequency and the proprieties of the core

number of turns of the primary for a pulsing dc voltage is N = to V/Bmax/Area/freq/2

above this voltage or bellow this freq the core will saturate

so the maximum pulse on voltage for your maximized transformer is the ratio between this turns of the coil and the primary and the input voltage

during pulse off the colapse voltage will depend on the resistance across the primary (for a simpler control of it) and the current it was charged to, and consequently the secondary coil will receive this voltage in proportion to the turn relation again.. so its a multiplification effect...flyback

If the secondary has a blocking diode like a flyback the pulse on is blocked so no current flow and thereto the collapse will be maximum since the secondary coil didnt developed any contrary magnetic field that would cancel the energy accumulated into the core by the primary

the collapse voltage depends on your switching level of protection...and of course the resistance across the primary... the voltage that will apear across the primary during pulse off it V=I*R this voltage is many times able to burn your switch...

to prevent that the switch must be protected.. TVS and MOV techonlogy is available

to use them you must watch the amp rating and voltage rating i use them in series and parallel to increase the power proprieties

i get 1000v limit

remember you may be measuring the rms current so the peak may be more than twice your reading... watch this that can confuse you... the better way is to measure it on oscilloscope to get peak reading... if possible...

http://www.ieee.li/pdf/essay/practical_magnetic_design.pdf(http://xtronic.org/wp-content/uploads/2010/05/copper-awg-metric-table.jpg)