5 x LM338K

[moutoulos]

If I put 5 x LM338K (5A) parallel (like the circuit), I will have 25A power supply ??.

[audioguru]

Yes, if you don't adjust the output voltage very much.
The problem is cooling them. With a huge heatsink and high velocity fan, each one can dissipate only about 50W. So the 5 of them can dissipate only about 250W and therefore the max difference between the input voltage and output voltage is only 10V.

If you want a high-current regulator with an adjustable output voltage then you need a switching regulator which doesn't heat nearly as much.

[moutoulos]

Thank's Audioguru ;)

[Shahriar]

Dear moutoulos

It would work but I think  something is happening.
Those regulators are not Exactly the same. for example the first output is 5.25V and the other is 5.20V.
then we would have a current from the first IC into another on.
this also causes that all reulators do not give the same power.
If you connect the output of each one through a diode then maybe some of the problems get solved. (MAYBE)
but using a regulator and a Power transistor will be much more better.

HTH - Shahriar

[moutoulos]

Dear Shahriar

To me appears this reason that you say. Simply I have already a regulated power supply 20A, and I wanted to make a half simpler, without transistor, pcb  and the rests. I do not know him I will think. In any case you I thank too much.  :)

My english is...not good :-\ sorry.

[audioguru]

Shahriar,
An LM338K is a regulator in a power transistor's metal case. While a 2N3055 transistor is rated to dissipate 115W when its case is somehow kept at 25 degrees C, the LM338K is rated to dissipate 100W for the same condition. Of course heatsinks aren't perfect and heat-up, so the power dissipation must be reduced.
Power transistors added to a plastic regulator won't help much.

[Shahriar]

Dear Audioguru

Sorry, I didn't mean that you can draw 25A from One power transistor. (I had Mis-spelled  ;D)
If you want to draw 25A you have to use 4 or more 2N3055 (depending on Input voltage and output voltage, {VCE}).
anyway if the your power supply works fine as much as you expect, then No problem, that's yours ;)

Shahriar