<html> <head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <style type="text/css" style="display:none"></style> </head> <body dir="ltr" style="font-size:12pt;color:#000000;background-color:#FFFFFF;font-family:Calibri,Arial,Helvetica,sans-serif;"> <p><br> </p> <p>Interesting theory David, that sounds like it may be exactly what happened.<br> </p> <p><br> </p> <p>Mike<br> </p> <p><br> </p> <p><br> </p> <div id="Signature"> <div name="divtagdefaultwrapper" style="font-family:Calibri,Arial,Helvetica,sans-serif; font-size:; margin:0"> <div> <hr> </div> <div>Michael S. Briggs, PhD</div> <div>UNH Physics Department</div> <div>(603) 862-2828</div> <div> <hr> </div> </div> </div> <div style="color: rgb(33, 33, 33);"> <hr tabindex="-1" style="display:inline-block; width:98%"> <div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> David Tiefenbrunn <davidtief@comcast.net><br> <b>Sent:</b> Friday, May 26, 2017 12:40 PM<br> <b>To:</b> noaddress@drmm.net; elec-trak@cosmos.phy.tufts.edu<br> <b>Subject:</b> Re: (ET) Aaargghh!!!!</font> <div> </div> </div> <div> <div>I'm not 100% certain, sinceI never tried running a ferro resonant charger with no load, but that could have over voltaged the diodes, causing one to fail shorted. Turning the disconnect back on now applies a battery capable of over 300 amps to a low resistance load. Smoke.</div> <div><br> </div> <div><br> </div> <div><br> </div> <div id="composer_signature"> <div dir="auto" style="font-size:88%; color:#364f67">Sent from my Verizon 4G LTE smartphone</div> </div> <br> <br> -------- Original message --------<br> From: David Roden <etpost@drmm.net> <br> Date: 5/26/17 11:53 AM (GMT-05:00) <br> To: elec-trak@cosmos.phy.tufts.edu <br> Subject: Re: (ET) Aaargghh!!!! <br> <br> On 26 May 2017 at 11:13, bushman165s--- via Elec-trak wrote:<br> <br> > when you finally closed the disconnect, a surge of current caused the<br> > diode/s to short. <br> <br> I don't see what you're getting at here. The tractor was off. Why would a <br> current surge result from closing the disconnect? What am I missing?<br> <br> The diode(s) probably shorted when Michael applied power to the charger. <br> Shorted diodes would be a short circuit right across the full transformer <br> secondary, making for a BIG load. That's what caused the odd sound and the <br> breaker trip.<br> <br> > I have been using solid state rectifiers to replace the diodes for a<br> > while now. <br> <br> I don't quite understand this. Granted, I'm an old guy, but in the <br> nomenclature I learned in the 1960s and 1970s, that's what silicon diodes <br> like the original 1N3493 are -- solid state (semiconductor) rectifiers.<br> <br> Maybe I'm just not familiar with these modules. Can you provide a weblink? <br> Thanks.<br> <br> > The rectifiers are 10x quieter, also.<br> <br> Don't see how; nothing in a rectifier makes noise. <br> <br> As I said, I've never used the ET charger, but I would expect that any noise <br> would come from the transformer. It's good old 60 Hz hum. <br> <br> Louder hum (more like a buzz, really) is characteristic of a classic battery <br> charger ferroresonant design, which the GE uses. <br> <br> That's what the cap is for. Briefly, with the extra transformer winding, it <br> introduces magnetic saturation in the core to stabilize the output voltage. <br> <br> Here's a much better and more complete explanation than mine above: <br> <br> http://www.electroncoil.com/ferroresonant_transformers.php<br> <br> If the transformer is making less noise, I'd worry that it may not be doing <br> what it's supposed to do.<br> <br> <br> <br> <br> David Roden - Akron, Ohio, USA<br> <br> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = <br> Note: mail sent to the "etpost" address will not reach me. To send <br> me a private message, please use the address shown at the bottom<br> of this page : http://www.evdl.org/help/<br> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = = =<br> <br> <br> <br> <br> _______________________________________________<br> Elec-trak mailing list<br> Elec-trak@cosmos.phy.tufts.edu<br> https://cosmos.phy.tufts.edu/mailman/listinfo/elec-trak<br> </div> </div> </body> </html>