Isolation transformer Wanted - Page 1
Forum section: electronics / general

author: Scutarius
author_rank: Regular Contributor
timestamp: February 14, 2014, 04:42:30 am
content: I am looking for an isolation transformer 110v-110v (100VA or more)Do you know any source in China? Normally I can find anything on ebay, alibaba etc but It looks like they only sell for 100+ unitsThank you

author: CM800
author_rank: Frequent Contributor
timestamp: February 14, 2014, 07:59:21 am
content: What country are you in? if your in the uk, just pick up a site transformer or 2?

author: cybermaus
author_rank: Frequent Contributor
timestamp: February 14, 2014, 10:09:22 am
content: Well, he is asking for 110:110, so probably he is on the other side of the water.Those site transformers you mention are typically 240V to 110V, as it appears a UK safety requirement to work with lower voltages on building sites.I have never opened one, or measured one, but while some of them are advertized as "isolation transformer" on the label they also say "centre tapped to earth". The centre tap cannot be on the primary side (as it would short out a one of the 240V leads) so must be on secondary side, which means they are not isolated.Personally, I do believe earthed with RCD/GFCI is safer then isolation anyway, so I think UK safety counsel or whatever they are called made the right decision, but "centre tapped to earth" means they are not true isolation transformers.Edit: I just realized: if they are centre tapped, and still have 110V pole to pole, it means only 55V to pole to earth, both pins hot. Or rather, both pins tepid.

author: mrflibble
author_rank: Super Contributor
timestamp: February 14, 2014, 01:07:54 pm
content: You could also get two identical 110:24 (or whatever is available) transformers and put them back to back. Depending on what you can get your hands on, this can be the cheapest solution. That, and you can be pretty sure it is isolated.

author: orion242
author_rank: Unknown
timestamp: February 14, 2014, 01:21:43 pm
content: Quote from: ee.jcesar on February 14, 2014, 04:42:30 am?First link searching Ebay 500va < $50 more than 1 available.http://www.ebay.com/itm/Powertronix-Medical-Grade-120-230V-500VA-Toroid-Isolation-Transformer-MIU-500-/271375796405?pt=BI_Circuit_Breakers_Transformers&hash=item3f2f4208b5I got this one a few months ago....http://www.ebay.com/itm/Powertronix-Medical-230V-or-120V-500VA-Toroidal-Isolation-Transformer-MIU-500-/271399036788?pt=BI_Circuit_Breakers_Transformers&hash=item3f30a4a774

author: Scutarius
author_rank: Regular Contributor
timestamp: February 14, 2014, 02:12:02 pm
content: QuoteQuoteI am from Latinamerica, and shipping from the US is very expensive for those items.QuoteYes, I thought that, but what problems can I face? I can only think in power losses.QuoteI would probably buy this one and ask a friend in the states to take care of it.

author: mrflibble
author_rank: Super Contributor
timestamp: February 14, 2014, 02:29:23 pm
content: Quote from: ee.jcesar on February 14, 2014, 02:12:02 pmDon't think problems, think "problem solved".But yes, you will get some more power loss compared to the single transformer with single core solution. But since you specified 100 VA that shouldn't be that much of an issue, unless this is for full load 24/7 operation.

author: Scutarius
author_rank: Regular Contributor
timestamp: February 14, 2014, 02:36:45 pm
content: Quote from: mrflibble on February 14, 2014, 02:29:23 pmThank you, I will give it a try. Well I will be searching more online before doing this work around.

author: grumpydoc
author_rank: Super Contributor
timestamp: February 16, 2014, 10:19:55 am
content: QuoteThe secondary on these transformers is 55-0-55 with the centre tap earthed so that the differential between earth and either of the conductors is only 55V to increase safety.