12 vdc to 18 vdc isolated P-P

[jamesrnz]

ok
i used a simple rc snubber here from drain to b+ although it seem to matter whether it went to gnd.


0.01uf and 3.9 ohm at 2w.

how much ringing and turn off spike is appropriate?

[Eva]

Hey, this is looking nice, at which load did you take the photo?

A few damped oscillations are ok, particulary if you can obtain them without too high losses in the snubbers.

It does not matter if the snubber goes to GND or to B+ as long as you have a short low impedance path from GND to B+ (obvious!)

You may find that turn-on EMI and ringing is easily reduced by reducing MOSFET turn-on speed.

[jamesrnz]

eva,

thanks, it is a result of your help and the other who contribute here.

this is at about 170 watts out for 30 minutes.

17.5 v a 9.5a , 2 ohm load.

the transistors and rectifiers get up to about 81f with a simple aluminum plate about 5.5x5.5x0.125.

the transformer gets to about 135f.


the windings are 66 wires of#36 which is 2640cm, which is 5.28 amps per 500cm, so i2r is getting too high.. i will have too add alot more wire if i am going to got to 42 amps.

( although i did hook it up to a 0.5 ohm load and the output dropped to 15.5 v at about 32 amps for about 3 secs before i took if off of the load, i'm allergic to plasma)

the snubbers are running about 95f.

(i have a little IR temp sensor)


i will rewind the transformer with more wires and spread them out. but im going to have to put a lot more on in order to get i2r respectable, since the inner windings wont cool well...........

[jamesrnz]

i wonder if i should use two of these power supplies at 20amp with the ft-140-77 with more wires and combine them in inductor with parallel windings,

i'm not sure i can get enough copper on this small core to handle the current i want. and a larger core would just get messy???

[jamesrnz]

iam adding a lot more wire to eachh core,, instead of 66 wires per turn i have crammed on 320

i will test this next week.......




i wonder if i should use two of these power supplies at 20amp each with the ft-140-77 with more wires and combine them in inductor with parallel windings,

[jamesrnz]

well i am going to get delayed.

i made another pcb

i made another transformer

BUT the BOSS called and I have to go back on the road for a few weeks, sooooo i am waiting to test the nigger transformer at least 25 amps only slightly warm is the goal............


standby , same bat-time, same bat-channel......

[Eva]

Hope to get news from you and this new prototype soon

[es44]

Originally posted by jamesrnz

i am waiting to test the nigger transformer

Oh dear, keyboard slips are quite common, but sometimes a little unfortunate

Cheers
Ebbe

[jamesrnz]

yep absolutely. i apologize to any one offended. should have been BIGGER....... fat fingers.


again sorry to anyone offended, none meant

[jamesrnz]

well i got stuck out on the road for a couple of months.

i will be back home in a week or two hopefully and after the honey doo's, i can get back to the project.


sooo... what would be the best ?

combine two switchers in parallel after the inductors?

or

combine two switchers in parallel after the transformer and two windings on the inductor?

or

parallell two transformers across one another using the same fets to drive and one inductor?