Powersupplies and the JLM calculator (edited)

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sr1200

Well-known member
Joined
Dec 6, 2010
Messages
2,094
Location
Long Island, NY USA
http://www.jlmaudio.com/ACDC%20Calculator.htm

if anyone has some time to school me on what I'm looking at here.  In particular the C/W rating and the total VA for the transformer. 
My numbers for arguments sake.  24 volt + rail @4amps, no secondary rail and the 48v at a half amp.  He says that if the CW rating is over 50 you dont need a heat sink on the regulators.  So if i make the power transformer AC 24-26 volt, i get a set of numbers (WELL below 50) if i put 18v AC i get HUGE numbers on CW.  Now would that be because im going to heat the hell out of the transformer instead of the VRs? What should I be looking to do here?  Where am I?  Who am I?  Why am I here?  What?!

EDIT:  I think my question basically relates to:  DO i need a couple of volts extra hitting the VR's?  If i use an 18vAC trasnformer im getting very little wasted voltage at the VR which is why my C/W is going up and more when i go higher AC on the trafo, so more waste more heat sink needed.
 
> DO i need a couple of volts extra hitting the VR's?

YES.

If your wall voltage were constant, you'd just wind the transformers for what DC you need. But Long Island Power or Light doesn't give you a steady voltage.

You need to be sure you have ~~3v excess on dim days.

You need to pick the sinking to handle the excess on over-volt days.
 
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