small crack in torroid!!future of torroid?

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see the pic
this is the use.
in smps.
 

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hey

thepower supply being used is only 500ma.is it possible that such insignificant supply unable to bring up any appreciable change in flux so as to give o/p????

the test corei used earlier was 4cm dia and it worked.i replaced this core but not working.4cm has no crack@all.
 
These cracks will reduce the permeability of the core, thus increasing magnetizing current and decreasing magnetizing inductance. It shouldn't be a big issue if the core is well clamped to minimize crack lenght, though.

By the way, this is how a transformer wound in the right way looks like, it features 6+6:12+12 turns and it's intended for low frequency usage in the 30Khz range:
An externally hosted image should be here but it was not working when we last tested it.
 
r u sure this big core is made of ferrite?
it can be iron powder and may cause saturation at a freq u were working with the small one .
i guess u got no scope , making things very difficult ...
check the supply voltage drop with a voltmeter while using the working core , then with this core . if with the big core the voltage drops drastically then its saturating i guess.
 
try to use a trimmer (or a potentiometer) instead of Rt (timing resistor) and play with the freq , in the same time look at the supply voltage till u get the smallest drop . dont go over 100khz and below 10khz , i guess .

on the other hand , man , that toroid is very big ! if u are trying to make a high power smps then u'll have some losses , so the current drawn when idle is also more then 500ma ....
i'm making a 500W smps and it needs 2 amps just to work :) without the load running from 12V .
the efficuency is never 100% so if lets say u are making a 500W smps with 90% efficiant running from 12V ....4 amps at idle will give u 48W of power loss (almost 10% out of 500W)


update :)
ok , now i saw your circuit :) and it looks like u are making high power (more then 100W i guess) smps , so 500ma is not good enough .....
 
this is my second smps.one already working in car.the same huge torroid was used in that one.i tested that smps in the college using monsterous dc supply and power res.that smps supplied 900w continous!!(al setup was cool)i didnt go furhter but believe that it could go further to bout 1600w.
that one had no crack.this one has.size is same.


trimmer idea is good,but i wil have to use 47k or 22k only bec the diodes r not so high freq tolerant.i have a five amp supply 12v dc at home.its holidays here so cant go to college b4 wed.

will do tests today.

ok , now i saw your circuit and it looks like u are making high power (more then 100W i guess) smps , so 500ma is not good enough .....
the similar torroid went upto 900w continous:)
 
forgot!!

what effects the saturation?does freq needs to b changed(by trimmer of course) to avoid saturation?actually my diodes have high i rating,high v rating but absolute max of 50khz.so don wanna blow them(very costly).
will do the high current power supply first,freq test afterwards(when u tell:))
 
reply reply reply reply.......................

used heavy power supply,but to no avail.the voltage drop is not significant,so saturation can b easily rulled out.
o/p is still 0.all other modules ok(hooked them to other places where they can work and they did)

advise plz:smash: :smash: :smash: :smash: :smash: :smash: :smash: :smash: :smash: :smash: :smash: :smash: :smash: :smash: :smash:
 
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