Hi
Good afternoon all.
My smps HF transformer secondary output is 12 volt 33 amp.
I want to increase voltage 24 volt . ampere 5 amp is sufficient for me.

Can i increase the secondary turns.
Secondary has multi strand, so can i do half the strands and double turns.
Or do i need to rewind primary winding too.
Please check the attachment

 

It largely depends on what Transformer You are talking about.

Not all Transformers are created equal,
some designs lend themselves to being easily rewound,
and others are simply impossible to modify.

Pictures would be a big help in this case.
.
.
.

 

It largely depends on what Transformer You are talking about.

Not all Transformers are created equal,
some designs lend themselves to being easily rewound,
and others are simply impossible to modify.

Pictures would be a big help in this case.
.
.
.

I have uploaded the pictures. Please check.

 

Depending on your smps you may not need to rewind the tranny. Instead, adjust the voltage feedback and uprate the output capacitor(s) for the higher voltage.

 

Depending on your smps you may not need to rewind the tranny. Instead, adjust the voltage feedback and uprate the output capacitor(s) for the higher voltage.

Thanks. Basically i am assembling a smps with ic UC3845B . In new circuit i want to use this transformer.
So for learning purpose i want to do this.

 

Hi
Good afternoon all.
My smps HF transformer secondary output is 12 volt 33 amp.
I want to increase voltage 24 volt . ampere 5 amp is sufficient for me.

Can i increase the secondary turns.
Secondary has multi strand, so can i do half the strands and double turns.
Or do i need to rewind primary winding too.
Please check the attachment View attachment 310779

Hypothetically, that should work. You shouldn't need any changes to the primary because you haven't changed anything on the primary side. If there's feedback then that will need changing.
Practically, it's a question if you can dismantle the transformer.
Firstly, you have to release the ferrite cores. That can usually done by heating it up until the varnish softens, but heat it too much and you will melt the bobbin.
Then, if it's a flyback transformer, it will normally be wound as a sandwich - primary-secondary-primary, so you will have to remove and rewind half the primary, unless you are very lucky and can separate the ends of the secondary winding.

Edit: for some reason, if I write primary;secondary;primary with colons rather than semicolons, the AAC website replaces the second "<colon> p" with an emoji that I didn't type.

 

Hypothetically, that should work. You shouldn't need any changes to the primary because you haven't changed anything on the primary side. If there's feedback then that will need changing.
Practically, it's a question if you can dismantle the transformer.
Firstly, you have to release the ferrite cores. That can usually done by heating it up until the varnish softens, but heat it too much and you will melt the bobbin.
Then, if it's a flyback transformer, it will normally be wound as a sandwich - primary-secondary-primary, so you will have to remove and rewind half the primary, unless you are very lucky and can separate the ends of the secondary winding.

Edit: for some reason, if I write primary;secondary;primary with colons rather than semicolons, the AAC website replaces the second "<colon> p" with an emoji that I didn't type.

Thanks

 

Hypothetically, that should work. You shouldn't need any changes to the primary because you haven't changed anything on the primary side. If there's feedback then that will need changing.
Practically, it's a question if you can dismantle the transformer.
Firstly, you have to release the ferrite cores. That can usually done by heating it up until the varnish softens, but heat it too much and you will melt the bobbin.
Then, if it's a flyback transformer, it will normally be wound as a sandwich - primary-secondary-primary, so you will have to remove and rewind half the primary, unless you are very lucky and can separate the ends of the secondary winding.

Edit: for some reason, if I write primary;secondary;primary with colons rather than semicolons, the AAC website replaces the second "<colon> p" with an emoji that I didn't type.

Hiii thats working. But transformer making humming sound . Ferrites core broken while assembling so i joint it by fevikwik ( a instant dry adhesive) so may be this reson for humming.?

 

Hiii thats working. But transformer making humming sound . Ferrites core broken while assembling so i joint it by fevikwik ( a instant dry adhesive) so may be this reson for humming.?

Humming? Perhaps it doesn't know the words. . . . . .
It should be operating at a frequency above your hearing range, unless you are a cat.
Any audible frequencies suggest that the feedback loop is unstable.
If you glued the ferrite with cyanoacrilite then it should be OK.

 

Every transformer have if force the 11-th grade physics course formulas a) V(2)=transformer constant * turn count b) max current=sum of wire cross section * max permitted current density. However specifism of altered frequency is - each strand diameter may categorically be under 0.6 mm, but better under the 0.3 mm. With these 3 laws may wind every core with existing primary. Yet if want to change primary as well, then transformer constant at 50 Hz is turns to Volt=50/S(cm2), however at SMPS frequencies turn count must be actual frequency / 50 Hz fold lesser and B(max) of ferrite / 1 Tesla fold larger as this formula states. Plus - for meandric signal the turn count must be 1.11 fold larger - remember that meander is more "poisonous" as sinwave.
And warm advice - condemn the every methodology based on inductance calculus - them ALWAYS lead to huge mistakes.

 

RE:<<assembling a smps with ic UC3845>> It means You have no ANY rational reason to deglue the ferrite. The approximately 20 turns may easily rewind on the already glued core. Its never the 200 turns or 2000 turns.