Blew another damn transformer on my Trane XB80

Unless the half wave rectifier is on the PRIMARY side. I don't see any evidence of that on any of the diagrams I saw, but is there something else on this furnace circuit? By code there cannot be

- but we don't know know this to be the case - or what is on the circuit if there is.

Reply to
clare
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To the OP... another long shot..

it looks like the primary of the transformer is wired in series with the door safety switch. Is it possible that the door safety switch is loose and arcing. This could cause a high voltage to appear at the transformer and cause the insulation to fail...

Mark

Reply to
Mark

Lots of ripple. If it were on audio circuit, lots of hum!!!!

Reply to
Tony Hwang

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Linked from

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That place even shows shredding of some engine blocks. They make shredding of bowling balls look easy!

Is a computer or some other electronic device ticking you off?

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They even shred shredders:
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Reply to
Don Klipstein

There won't be a rectifier feeding the primary of a transformer with DC. A transformer does not pass DC from one winding to another the way it does with AC.

Changing AC that transformers work with to DC that electronics work with has to occur downstream of the transformer.

I have yet to look at these diagrams, but is the circuit board powered by this tranny shown to "board level" as opposed to "component level"? If so, then the board can have, probably does have, a rectifier not shown in the diagram.

Reply to
Don Klipstein

On 4/12/2011 9:23 PM Don Klipstein spake thus:

With all the pontificating you've been doing here, Don, I would've thought you'd at least had glanced at the wiring diagrams the OP posted, way up there somewhere. Sheesh.

The controller is shown as a block. It most certainly has at least one rectifier on it, as it contains electronics that no doubt requires DC power to operate. Thought you'd have figured it out. (Not just a relay board.)

Reply to
David Nebenzahl

Having an extremely warped mind, I thought some Hollywood special effects guys should get together with a shredder company and make a very special YouTube video of an Islamic terrorist being tied up in a big burlap sack with a hog. The whole squirming mass would be dropped into a monster shredder and all the sound effects, blood and guts would be awesome. At the end, a disclaimer would read.... "No actual pigs were harmed during the production of this video" Of course the reaction would be the same as the nut-jobs who were upset about their Koran being burned and went around killing everyone they could find who they believed to be a Christian.

TDD

Reply to
The Daring Dufas

Interesting theory. One helpful piece of info which it's quite amazing we still don't have is what the currents are on both sides of the transformer. For saturation to occur I would think the transformer would have to be close to fully loaded. Which it could be, given the trends to lower cost, cheaper components, etc.

Reply to
trader4

Your idea tracks with one described by an acquaintance of mine.

He envisioned a web site, "stopthedesecration.com."

On the web site, a (masked) host is seen standing in a warehouse chock full of Wahabi-sanctioned Korans. The site promises that for every outrage committed in the name of Islam, some book (or a portion) will be desecrated! There is also a "catalog" of outrages and consequences (if I remember correctly).

  • Every anti-American or anti-western sign shown on TV = One page ripped out and stomped.
  • For every non-Muslim injured in the name of Islam = One entire Koran shredded.
  • For every non-Muslim killed in the name of Islam = One entire Koran shredded, mixed with pig blood and feces and flushed down a toilet.

Appropriate videos will be cataloged, each showing the offense AND the sanction in graphic detail. A continuous scroll appears on the screen: "Only YOU can stop the desecration! Do not permit your friends and family to harm others!"

Reply to
HeyBub

Ever seen: Salvadore Dali's Chaos and Creation ?possibly the first example of ... an abstract painting made using a motorcycle, popcorn and Pennsylvania pigs

I believe it had a similar disclaimer.

I have a friend who is working on a haunted house. These things take months to make. He's in charge of the special effects and an ex alter boy. I'll suggest it to him. The house, I believe, is in the Bible belt so it may appeal to the locals.

Jeff

Reply to
Jeff Thies

I fully understand that, byt what happens if, say, the Mrs plugs her cheap blow drier into the same circuit as the primary of the transformer is plugged in to, and she puts the blow drier on low (it uses a half wave rectifier to drop the power to the heater) - and you end up with a DC component on the primary - which saturates the primary without any increase in secondary (load) current or power.

I am very aware of that.

Again, fully aware that the circuit board WILL have a rectifier which is not shown on the diagram, and better than 95% chance it is full wave bridge rectifier. There are precious few solid state control devices that run on AC.

Reply to
clare

As I posted in an earlier post (not sure what values I used, but I'll run a scenario anyway), assuming a 2 ohm winding, a 2 volt DC component will cause 1 AMP of current to flow in the winding. IF that coil happens to be the primary of a 40va transformer, The full load current on that transformer is about 350ma, so the probability that 1 amp of current in the primary, with no AC voltage applied, would have more than saturated the core is pretty good. Add the quiescent current of the primary, and you have a saturated core. And that's just a 2 volt DC component on a 115 volt primary.

If the primary is 4 ohms instead of 2, you have half an amp with 2 volts, or 1 amp with 4 volts.

Doesn't take much to put 2 volts DC across a 115 volt line.

See

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for more information from someone who may have a bit more credibility than you guys may give me.

Reply to
clare

** A 40VA tranny designed for 120 volt 60 Hz operation has a primary resistance of 16 ohms.

Getting a 2 volt DC offset on a 120 volt AC supply takes some doing.

** Like hell.

For a 2 volt DC offset to exist, the peak voltage in one polarity must be

6.3 volts higher than the other.

With a typical impedance at the outlet of 0.25ohms, this equates to 25 amps peak load in one polarity and none in the other.

** I helped Rod write that article.

Toroidal trannys are very sensitive to DC offsets while regular E-core types are hardly bothered by them - the difference is that while the former has no air gaps in the core, the latter is full of them.

.... Phil

Reply to
Phil Allison

I don't remember the details, but I know quite a few DO work that way

- and they also used 12 volt DC blower motors, without a transformer, by basically using the heater element as a rheostat..

Reply to
clare

"Stormin Mormon"

** My 1600 watt "Black & Decker" hot air gun is made exactly like that.

.... Phil

Reply to
Phil Allison

Steve,

Not to be rude or anything, but a LOT of talk has gone on about your problem and I have not seen any further posts from you on the matter. No comments about any suggestions at all.

I'm not going to spend any more time on this thread until we hear back from the original poster with more information otherwise we are simply blowing smoke (sorry - couldn't resist).

John :-#)#

Reply to
John Robertson

Just mentioned elsewhere that I have a new transformer on order and I can't really do anything until that arrives. Rest assured I appreciate all the input and I'm taking it all into consideration. Thanks.

Reply to
Steve Turner

You bought the fuses, right? I DON'T want to hear about another blown transformer.

--Vic

Reply to
Vic Smith

With such indication even as described here giving low indication as to rectification having a 1-component bridge rectifier, 4 discrete diodes, a fed-with-center-tap 2-diode fullwave scheme, 2 separate diodes or a single 3-lead dual-diode used for that...

If the controller is only shown as a block, how well does it show the rectifier scheme, as in whether the rectifier's diodes are discrete individual diodes or integrated into one rectifier package?

If anyone here sees that noted to such extent that it's not a waste of my time to take a look there, please pipe up!

Reply to
Don Klipstein

"Vic Smith" Steve Turner

** Be real smart for the OP to purchase some OTHER 120/24 volt tranny and use it.

The things are a dime a dozen.

And fit a "slo-blo" 1/4 amp fuse to the primary.

.... Phil

Reply to
Phil Allison

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