[R-390] Possible source for isolation transformers?

Wed Jul 4 14:56:50 EDT 2007

A VARIAC does not isolate.  From what the other gentlemen on the list have indicated, the boxes advertised are an autotransformer (like a VARIAC but with a fixed tap point).  It, too, does not provide isolation.

I have a 1KVA isolation transformer that can be wired as 120/120, 220/120, 220/220, or 120/220.  I think it came from a medical device as well.  Very nice, but not something I'd want to pack in my luggage for a 2-week trip overseas.

Regards,

Barry - N4BUQ

 On Wed Jul  4 14:42 , "Patrick"  sent:

>I have purchased from eBay a couple of isolation transformes (CyberCare), 
>apparently for use in hospitals, they are great, very well built. The tag 
>says CyberCare Inc. Atlanta Georgia 30350. Also, in the 80´s I had an 
>assignement in Germany and the company supplied the assignees with 220 to 
>120 transformers up to 2500 Watts and a switch for 110 or 125 volts output, 
>they weigh a ton, but in my workshop, which I have 220" they work great as 
>isolation transformers, also I you do not have 220, they work backwards as 
>well.... Wouldn´t a variac also serve as an isolation transformer?? they are 
>frequently on eBay, I bought one a few years ago that was used in a teather, 
>it handles 5 KW and only paid $45.00 for it, output goes from 0  to 145 
>volts.
>
>Regards....Pat.
>----- Original Message ----- 
>From: "Bob Young" youngbob53 at msn.com>
>To: r-390 at mailman.qth.net>
>Sent: Wednesday, July 04, 2007 10:51 AM
>Subject: Re: [R-390] Possible source for isolation transformers?
>
>
>> My wife is from Lima, Peru and I bought a huge 220V-110V transformer very 
>> cheap there, I used it to power everything I had brought over including 2 
>> bass guitar amplifiers. I think it had a capacity of 1500 watts. (lived 
>> there for almost a year). I don't think it was an autotransfomer either, 
>> looked (and weighed) like a traditional transformer. They are available 
>> everywhere in Lima in hardware stores and other places. I would assume the 
>> same is true in most other countries given the amount of Americans who 
>> travel.
>>
>> Bob
>> KB1OKL
>>
>>
>>>From: Barry n4buq at knology.net>
>>>Reply-To: n4buq at knology.net
>>>To: r-390 at mailman.qth.net
>>>Subject: Re: [R-390] Possible source for isolation transformers?
>>>Date: Wed, 04 Jul 2007 09:04:47 -0400
>>>
>>>I'm curious as just to what's under the hood.  I suppose they can get away 
>>>with calling an autotransformer simply a transformer.  If it is truly a 
>>>transformer, though, I can't see how they can sell them at that price.
>>>
>>>If they are autotransformers, is this a better solution for 220V-110V 
>>>conversion than the little voltage converters available?  I belong to a 
>>>list of folks who have (or will) travel overseas and several ask from time 
>>>to time about what to use to power their various 120V appliances 
>>>(chargers, etc.) while overseas.  While a small converter is fine for 
>>>charging a battery or running a small device, I keep having to warn folks 
>>>who want to power their blowdryers, etc., from them.  I thought these 
>>>might be a better alternative; however, they'd certainly need the 1500W or 
>>>larger unit for such applications.  I know blowdryers are available in 
>>>220V models and that's probably the best way to go, but most folks aren't 
>>>going to do that so I keep looking for better options.  I've explained the 
>>>"best" solution is a step-down transformer, but it's unlikely anyone will 
>>>want to pack one of sufficient size in their luggage.
>>>
>>>I know its OT, but if anyone has any thoughts on this, I'd appreciate a 
>>>reply either on or off the list.
>>>
>>>Thanks,
>>>
>>>Barry - N4BUQ
>>>
>>>
>>>  On Wed Jul  4  7:51 , "Steve Hobensack"  sent:
>>>
>>> >Transformers for this application are almost always autotransformers.
>>>They
>>> >are smaller for a given wattage because there is only one winding (with
>>> >tap), and the common part of the winding can be downsized. They will not
>>> >function for isolation. They can be used either for step-up or 
>>> >step-down.
>>> >...Steve...N8YE
>>> >
>>> >Knowing the leaky filters won't run on GFI circuits and are probably not
>>> >all that safe when used on non-GFI or non-isloated circuits, I think
>>> >some folks may be looking for isolation transformers.  While searching
>>> >for voltage converters for overseas travel, I found these:
>>> >
>>> >http://www.eastwestintl.com/proddetail.asp\?pid=2625
>>> >
>>> >They state that they are transformers, not just converters, and that
>>> >they can be configured to run either 110-220 or 220-110.  I wonder if
>>> >these could also be wired for 120-120 and used as an isolation
>>> >transformer.  If not, if someone has 220V in the shop, it might be a
>>> >good way to power an R390[A].
>>> >
>>> >If you back up a page, they have a variety of transformers ranging from
>>> >100W on up.
>>> >
>>> >Just thought I'd pass this along.
>>> >
>>> >Barry - N4BUQ
>>>
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