Guillermo, Rich is correct. The transformer can be de-rated some in most amateur applications. The ratings are known as ICAS (Intermittent Commercial and Amateur Service), and CCS (Continuous Commercial Service). Most amateur amps fall under ICAS. Here the size can be cut back by derating the current carrying capability of the wire in the transformer coil. You still have to have a certain amount of iron in its core, but by reducing the wire size, a core laminate with smaller windows can be used. This is because it takes a smaller window in the core for the amount and size of wire in the coil. By using a smaller lam, you gain in weight savings. The central core size in square inches has to be the same so the transformer will not go into saturation. This can also be dropped in size by using a laminate steel with a higher flux density. The only problem is, when doing this, and raising it's efficiency, the cost goes up a good bit. The most efficient core would use a laminate steel like M-6 (Hipersil) to M-2, but a cheaper, and almost as good core can be made with M-19 steel, with not that much of a difference in losses. The price difference between M-19 and M-6 is almost X 2. M-22 will also work with just a shade more losses, again with a price savings, but the weight will go up slightly as the flux density drops. The major difference in ICAS to CCS is that CCS is designed for 100% usage, or brick on key transmitting. A CCS amp is designed to be under load 24 hours a day. ICAS has a time limit like 5 minutes on and 5 minutes off to allow the transformer to cool off. ICAS is not for a continuous load. The main two differences then between ICAS and CCS is using a wire size of around 700-800 cir. mils per ampere for ICAS and 1000-1100 cir mil per ampere for CCS. I think if I recall that is about 2-3 wire sizes difference without looking at a chart. Best, Will ----- Original Message ----- From: R@contesting.com, Measures To: GGLL Subject: Re: [Amps] Transformer spec's for linear amplifier - added Date: Thu, 7 Jul 2005 06:35:05 -0700 > > > On Jul 7, 2005, at 4:00 AM, GGLL wrote: > > > Having the need of a 2500VDC @ 350 mA maximum current power supply, and > > planning to use a full wave voltage doubler, how can I establish the correct > > current rating for the transformer?. > > A good clue is the R of the secondary winding. This is discussed on my > Web site. Another consideration is whether the current will be > continuous - as for FM broadcasting - or intermittent - as for > voice-SSB, where the average current is c. 30% of the maximum current. > > > It should be nearly 930 VAC and exactly > > 700 mA of current, or can I reduce somewhat its current rating > > (taking in care > > amateur, CW/SSB use, also AM at reduced carrier) so as not to expend more $$ > > than really needed?. > > > > My question is oriented to duty cycle, so , if possible and > > advisable, how can > > I lower current ratings to save costs. I've read in many articles (all for > > amateur use, with transformers already salvaged from TV sets, and so) where > > smaller current ratings where used instead of theoretical ones. > > > > Thanks in advance > > > > Best regards > > Guillermo - LU8EYW. > > > > _______________________________________________ > > Amps mailing list > > Amps@contesting.com > > http://lists.contesting.com/mailman/listinfo/amps > > > > > > > > Rich Measures, 805.386.3734, AG6K, www.somis.org > > _______________________________________________ > Amps mailing list > Amps@contesting.com > http://lists.contesting.com/mailman/listinfo/amps -- ___________________________________________________________ Sign-up for Ads Free at Mail.com http://promo.mail.com/adsfreejump.htm