My own experience with a ferroresonant transformer was with a simple battery charger probably 10A at 14V (140W). I don't recall that it got noticeably hot. If dissipation is about 20% of full load, that would have been about 28 watts - but the unit was bolted to a steel vehicle body, which took away a lot of heat.
But this baby that Rick is talking about... 24V at 50 to 75 amps? Assuming 24V at 65 Amps, that's about 1500 watts, and 20% of that would be about 300 watts, which can make something very hot. If the unit was not bolted down to something that would take the heat away, then air convection would have to do it, and the thing could get pretty darn hot. Probably it was just on the floor, or on a wooden bench for this test. I would figure that the unit is designed to be mounted on some chassis and in some cabinet, which would act as a heat sink. If it gets too hot to comfortably hold, then put a fan on it. 300 watts dissipation... Rick, you said it drew about 0.9A unloaded, is that at 240V? That could still be as much as 200 watts dissipation, although I don't know about the phase angle / power factor. One thing to watch out for with a ferroresonant transformer is line frequency. The output voltage is approximately proportional to line frequency, so if you're on a generator, it could vary a bit. And don't expect good charge regulation on 50Hz if the transformer was designed for 60 Hz, and vice versa. I learned that the hard way - and I am glad that I wasn't the one who designed that system, because I might have made the same mistake. There I was looking at the system that had worked OK Fine in the USA, and it just didn't work overseas - and then I noticed that the musical pitch of the AC hum was wrong. Arrrgggh, 50 Hz!!! And the system was going to be used in some places that had 50 Hz power, and other places that had 60 Hz power... Fortunately there were switching battery chargers available at that time, and the project survived. Bacon, WA3WDR ----- Original Message ----- From: "W5OMR/Geoff" <[EMAIL PROTECTED]> To: "Discussion of AM Radio" <[email protected]> Sent: Sunday, May 07, 2006 7:14 AM Subject: Re: [AMRadio] Ferroresonant transformer revisited > Jim Candela wrote: > > >Rick, > > > > The ferroresonant transformer is not really > >resonant at all since the winding that feeds the > >capacitor is wrapped around a portion of the core > >that is a saturable reactor. Resonance and saturable > >reactors don't really go together, but in this case we > >do have circulating energy in a ferroresonant > >transformer which consumes about 20% of the VA rating > >of the device. So for a 1 KVA ferroresonant > >transformer the power draw when unloaded may be about > >200 watts, and this is pretty much a constant. > >Therefore with a 1 KVA load, the power input would be > >1.2 kva. Every line cycle runs the core into > >saturation, and this creates eddie core losses, heat, > >buzz, and a quasi square wave output. The output is > >not a sine wave unless yours has a harmonic filter. > >Therefore a true RMS meter is needed to accurately > >measure the AC voltage. > > > >These are really neat devices using very old > >technology. > > > > which covers everything *except* what Rick asked, Jim (grinz). > > How hot is the darn thing -supposed- to get? I, too, wouldn't think > that it's hot enough just sitting there, with no load, that you couldn't > put your hand on it.. > > -- > -Geoff/W5OMR > > __________________________________________________ ____________ > AMRadio mailing list > Home: http://mailman.qth.net/mailman/listinfo/amradio > Help: http://mailman.qth.net/mmfaq.html > Post: mailto:[email protected] > AMfone Website: http://www.amfone.net > AM List Admin: Brian Sherrod/w5ami, Paul Courson/wa3vjb >
