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Old 31-12-2010, 18:13   #1
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Hammond 3 kva ( Isolator ? )

I've got a Hammond 3 kva unit onboard, stamped ES2J. It's been fine until the last couple days, never buzzing or getting warm to the touch. Then about four days ago, after hooking up to shore power for nearly a week after a year an a half of generator/solar power, it started getting extremely hot to the touch and making a dreaded (to me, at least) low/medium pitched buzzing sound.

The voltage coming out was the same that was going in (110 in, 110 out), so I don't quite understand what happened. What we did, since we're in 220v Philippines, is use a 2kw stepdown transformer (220v to 110v) between shore power and the Hammond, and this worked great for about four or five days before it started heating up. The Hammond says 120v in/120v out on the plate, but I can't find much information on this unit right now, and my internet connection doesn't work too well at the moment, I'm assuming due to decreased bandwidth from the holidays here.

I've got two questions. First, what exactly is the Hammond unit? Is it a transformer or an isolator, or both? Neither? Second, why do I need it? It seems to me that if I'm using a functional stepdown transformer, or 'directly' plugging my inverter into native 110v land, it would be ok so long as there aren't ridiculous voltage spikes.

I don't understand very much about this thing. Thanks for any help!

P.S. - if you reply in the next day or two, please include the body of text from whatever reference sites you suggest I check. I can't seem to load more than a handful of sites right now, but thankfully CF is one of them
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Old 31-12-2010, 21:56   #2
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Have you added any AC equipment. Maybe you are overloading the isolation transformer. I couldn't find much information on it but I think it is a constant voltage isolation transformer. I did find the part number ES2J listed in the catalog general information but couldn't find the item specs. Sorry.
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Old 01-01-2011, 05:40   #3
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It's an "Isolation Transformer".

The transformer hum is caused by the expansion and contraction (vibrating at twice the source frequency + some harmonics) of the core laminations when magnetized.

All devices that use electricity give off waste heat as a byproduct of their operation. Transformers are no exception.
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Old 01-01-2011, 06:16   #4
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Quote:
Originally Posted by NotQuiteLost View Post
it started getting extremely hot to the touch and making a dreaded (to me, at least) low/medium pitched buzzing sound.
Guess:
1. Overloading
2. Eddy (Foucault) current in the core of the transformer. Check the core for visible sign of rust between the laminations. Can be cured by the careful use of WD40 otherwise it is a throw away.
Question 2: search this forum for isolation transformer
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Old 06-01-2011, 04:30   #5
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Thanks everyone for the replies. I'm still a bit confused why it made such a rapid deterioration from silent/cool-to-the-touch to buzzing and hot enough to burn your hand, but it does look like there's a little bit of rust on the outer copper(?) laminated plates that's made its way through the plates in some places on the edges. It's quite a chore to undo the whole thing, but I'm guessing it's just a 'toss it' situation.

If I had been running 220v into it, it would have made sense to have so much excess heat. But I was running 110v in and it was spitting 110v out. Am I missing something obvious regarding electricity? I guess I didn't even check the Hz in/out. Is that what it's regulating?
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Old 07-01-2011, 02:34   #6
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Quote:
Originally Posted by NotQuiteLost View Post
I guess I didn't even check the Hz in/out.
A purely 60Hz transformer is not suitable for use on a 50Hz supply.
Quote:
Originally Posted by NotQuiteLost View Post
What we did, since we're in 220v Philippines, is use a 2kw stepdown transformer (220v to 110v) between shore power and the Hammond,
If your step down transformer is an isolation transformer then you donít really require the ďHammondĒ(no need for two transformers, one after the other).

Quote:
Originally Posted by NotQuiteLost View Post
Am I missing something obvious regarding electricity? I guess I didn't even check the Hz in/out. Is that what it's regulating?
Normally an isolation transformer does not regulate anything.

Quote:
Originally Posted by s/v Jedi View Post
Actually, an isolation transformer galvanically isolates your boat from all shore power conductors.. ground, neutral and hot(s). It not only provides protection against galvanic corrosion, but is also a safety device unmatched by anything else.
cheers,
Nick.
This Forum provide some useful information regarding electricity but not as much that a good trade level book on electrical principles.
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