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Title: 5 V Filament Xfermer Post by: KB2WIG on March 15, 2007, 02:20:15 PM I am in posession of a 120/5 filament transformer. She is rated for 60 Amps.... What i'd like to do is get 10 volts out of it.... and maybee ~20A. Any usefull advice?? klc
Title: Re: 5 V Filament Xfermer Post by: n2bc on March 15, 2007, 02:28:23 PM If it's a non-potted E/I lamination job, just rewind the secondary. Twice the number of turns with #10 or #12 wire.
Title: Re: 5 V Filament Xfermer Post by: KB2WIG on March 16, 2007, 07:42:07 PM I was hopeing to see if anyone had done somthin like hookup to 220 v to get 10v out. Rewinding is an option but i didn't want to go that way fer a few reasons... I've actually got (2) 5v/50A xfermers so i'll get ~10V/100A for my mad design... Thanks......... klc
Title: Re: 5 V Filament Xfermer Post by: nu2b on March 17, 2007, 01:11:28 AM "I've actually got (2) 5v/50A xfermers"
This is 250 volt-amps per transformer and limited by the core size. If you rewound it perfectly you could get 10v/25A out of one xfmr. Since you have two transformers, put the two 120V primaries in series (phased properly) across 240 vac. The two 5V secondaries put in series would then give you 10V/50A. You didn't mention if you were building a welder, using it for filaments or if you were trying to get dc out. If DC, the diode bridge percentage loss at only 10V on the secondary will be significant. Also, the amount of storage cap required for significant filtering would be prohibitive not to mention the associated step start requirements. Regards, BobbyT Title: Re: 5 V Filament Xfermer Post by: KB2WIG on March 17, 2007, 02:04:34 AM B. T. , thanks fer the input..
Oh tay. I've got an old home brew i'm reverse edugessing. (2) 813 in pp modulated by (2) 810. Thats a total fil. load of ~200 watts. What I was thinking was to lower the "fil. weight" by 1/2; not needing all that iron from both xformers (they are about 4X4X8 inches). Thats the genesis of placing 220 on the primary... If I rewound them, thats when I find a carload of 4-400A's .... .. klc Title: Re: 5 V Filament Xfermer Post by: n2bc on March 17, 2007, 01:41:54 PM You need two transformers anyway - or at least two very well isolated secondaries. You cannot run the 813s and 810s on the same winding as they are directly heated... the filament is the cathode.
Title: Re: 5 V Filament Xfermer Post by: KB2WIG on March 17, 2007, 03:00:43 PM " You need two transformers anyway - or at least two very well isolated secondaries." yr right... after thinking 'bout it, thats the last thing I need with a push - pull 813 rf deck ... I got the rig as a "kit of parts" with a few extra parts thrown in. This makes the reverse guessing a little more interesting. The basic design looks like it was taken from an RCA tube manual and a ARRL Handbook. In the pile i've got a pair of 6.3v 20A stancors. It looks like they were used for the 813s' so i'll try them with a variac. AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
The mod deck has the fil xfermer on it, so there goes that problem... along with the low level audio amp pwr supply... that werked out nice... I think i'll start cooking them later on tonight. klc |