S-100 power supply transformer

Date: Wed, 20 May 2009 15:07:57 -0700 From: hilpert at cs.ubc.ca To: General at invalid.domain Subject: Re: S-100 power supply transformer A slightly different take on this transformer requirements issue.. Hammond used to (perhaps they still do) provide a piece of paper with every transformer, listing part numbers and specs. Included on the paper was a table for voltage and current factors for basic rectifier/filter circuits: (extract) Rectifier Filter Voltage Current VA ------------------- ------ ------------------ ---------------- ----------------- Half-wave cap in DCV = ACV * 1.16 DCA = ACA * 0.38 DCVA = ACVA*0.44 Full-wave center tap cap in DCV = ACV * 1.25/2 DCA = ACA * 1 DCVA = ACVA*0.63 Full-wave bridge cap in DCV = ACV * 1.25 DCA = ACA * 0.56 DCVA = ACVA*0.7 AC values are RMS; VA figures I added in. They don't say precisely how these figures were arrived at, but reality is a little different than theory (e.g. 1.25 vs 1.414 for the voltage output from the filter, don't know whether that's reduced due to R losses or an average with ripple under load). I take it these values were provided as guidelines, as complete design takes into account C size, tolerable ripple, etc. -- TI published "The Voltage Regulator Handbook" in the 70's, which covers a lot of design issues for linear power supplies. Even it references a design procedure from 1943 (Schade graphical techniques) for the rectifier/filter design.