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Need input for the impossible

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goofeedad

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I'm sorry if this sounds lengthy but, I was told in earlier posts that I didn't give enough info. and don't worry about stating as much info as possible.

OK, before I start I know this sounds impossible so please don't slam me.

I have built a fog device that uses 4 mist generating transducer drivers that require 36VAC. I installed a 110VAC to 36VAC transformer with a fan to cool the transformer. I have the 36VAC for the driver circuits and a 12VDC supply for the fans going through a relay that turns everything on when my control module (single unit, purchased from a seperate supplier) signals to turn the device on.
Here it is. All of these electronics sit very close to water (in my prototype version only). While running one day I saw a fast bright blue spark, it appeared to be at the relay but, I'm not totaly sure. I immediately turned everything off and checked for water and shorts. There was a little water, a few droplets in the bottom of the case but everything looked good. I dried everything with towels and a hair dryer. Hours later I turned the device back on and the driver circuits didn't make a mist / fog. I checked all the components and the ONLY thing that I was able to find was that the transformer was now putting out 41.8VAC.

That in itself sounds pretty much straight forward, I agree. Sounds like I blew my transformer. I recieved another identical transformer from the same company and "before" hooking it to my device I checked the VAC output, it was also 41.8VAC. I called the supplier and they checked one of their transformers they pulled from their stock, it read 41.8VAC as-well.

The supplier is very confused and is ordering the trans schematic, they've tested the trans at 119VAC that I'm getting from my house line, they've tried useing the trans in every way they could think of and it still puts out 41.8VAC.

The trans is part #104417 from Jameco.com a 36VAC trans. It has 2 seperate windings in the primary core since there are actually 2 windings. There are 4 inputs 2 ins and 2 outs for the AC. Your suppose to connect the terminals 1 & 3 and terminals 2 & 4 to the AV in. and the output has 3 terminals with the center terminal used to get an 18VAC.

The impossible thing is, if you haven't got it yet, is one of 2 things. 1. Why would my circuit work with the supposed given 41.8VAC that the first trans probably put out and not now. OR 2. If the first trans actually started with 36VAC then was shorted to give 41.8VAC, why does my second trans as-well-as the transformers that the supplier has on their shelf read the identical 41.8VAC when supplied with 119VAC?

Sorry for over stating my problem but, any help would be appreciated.
 

Sceadwian

Banned
All transformers put out a higher voltage than the one listed when it's not loaded. The 36V AC it's rated as when it's running at it's rated current, perfectly normal. Since this is a mist generator you need to completely water proof everything or this is just gonna happen again. I wouldn't be so sure that the transformer was the part that was bad, you're probably replacing a good part.
 
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crutschow

Well-Known Member
Most Helpful Member
41.8VAC is the normal unloaded transformer output voltage. The 36VAC is at the rated load which is less due to IR drop in the transformer windings. If you apply the rated load to the transformer is should measure reasonably close to 36V.

The water likely had no effect on the transformer. If something failed, it's likely elsewhere.

Edit: Sceadwian you beat me by a minute.
 
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goofeedad

New Member
Yep! I agree, but, when I tested my original transformer the unloaded output was 36VAC and the center output read 18VAC. The tech support agreed with me and all of their testing also showed this. I even asked the "obvious" (not to put any posts down). I asked, doesn't the fact that the transformer has no load, change the unloaded output? He said there should be 36VAC at an output of 1.5A.

Incase you and I are right I will redo my circuit with a totaly new driver circuit and see if that works.

P.S. Just this second I got a call from Jameco tech support. I will post any news he gives me.
 

crutschow

Well-Known Member
Most Helpful Member
It's not reasonable that a practical transformer output would not change with load, so if it had 36VAC output a no-load, then it would be noticeable less at full-load, 10-15% change is not unusual.
 

goofeedad

New Member
It's not reasonable that a practical transformer output would not change with load, so if it had 36VAC output a no-load, then it would be noticeable less at full-load, 10-15% change is not unusual.
True, the tech support stated that the test was done at a 1.5A load.

I'm still confused by what tech support is telling me but, it's me not them. He said that, he now has the spec sheet for the inputs and will do a full series of test in the morning. When I find out something all of you will be informed. Thanks.
 
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