Re: (ET) Aaargghh!!!!

From: David Tiefenbrunn <davidtief comcast net>
Sent: Friday, May 26, 2017 12:40 PM
To: noaddress drmm net; elec-trak cosmos phy tufts edu
Subject: Re: (ET) Aaargghh!!!!

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.

Sent from my Verizon 4G LTE smartphone

-------- Original message --------
From: David Roden <etpost drmm net>
Date: 5/26/17 11:53 AM (GMT-05:00)
To: elec-trak cosmos phy tufts edu
Subject: Re: (ET) Aaargghh!!!!

On 26 May 2017 at 11:13, bushman165s--- via Elec-trak wrote:

> when you finally closed the disconnect, a surge of current caused the
> diode/s to short.

I don't see what you're getting at here. The tractor was off. Why would a
current surge result from closing the disconnect? What am I missing?

The diode(s) probably shorted when Michael applied power to the charger.
Shorted diodes would be a short circuit right across the full transformer
secondary, making for a BIG load. That's what caused the odd sound and the
breaker trip.

> I have been using solid state rectifiers to replace the diodes for a
> while now.

I don't quite understand this. Granted, I'm an old guy, but in the
nomenclature I learned in the 1960s and 1970s, that's what silicon diodes
like the original 1N3493 are -- solid state (semiconductor) rectifiers.

Maybe I'm just not familiar with these modules. Can you provide a weblink?
Thanks.

> The rectifiers are 10x quieter, also.

Don't see how; nothing in a rectifier makes noise.

As I said, I've never used the ET charger, but I would expect that any noise
would come from the transformer. It's good old 60 Hz hum.

Louder hum (more like a buzz, really) is characteristic of a classic battery
charger ferroresonant design, which the GE uses.

That's what the cap is for. Briefly, with the extra transformer winding, it
introduces magnetic saturation in the core to stabilize the output voltage.

Here's a much better and more complete explanation than mine above:

http://www.electroncoil.com/ferroresonant_transformers.php

If the transformer is making less noise, I'd worry that it may not be doing
what it's supposed to do.

David Roden - Akron, Ohio, USA

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