Transformer query

The STEU 320/23 transformer shown here: http://www.block-trafo.de/fileadmin/productpdf/STEU.pdf
is 320 kVA. As the transformer has 2 x 115 Volt outputs, can anyone tell me
if the 320 kVA rating is 160 kVA for each output. If this is so, and I need 320 kVA, can I parallel up the two secondary outputs. Also, would you normally earth down one side of the secondary.
TIA
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sorry, that should be VA, not kVA.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
BIGEYE wrote:

I rather think that you have lost a decimal point somewhere. 320kVA transformers tend to weigh a tad more than 4kg..
But, yes, for that transformer, I would expect to be able to parallel the output windings.
Whether one side of the secondary would be earthed is down to the application. That would also determine whether you really need an isolation transformer rather than an autotransformer - the latter should represent a very significant saving..
As always, the people to ask are the manufacturer: eg snipped-for-privacy@block-trafo.de
-- Sue
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Sent an enquiry to them a couple of days ago, no reply as yet.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Palindrome wrote:

Yes, and you might like to also consider building/ construction site transformers from e.g. Screwfix. These have an earthed centre tap, giving 55-0-55V (probably rated for 230V input now, so giving out 115V instead of 110V on 240V) They are double-wound safety isolating transformers, so the centre tap could safely be "un-earthed", depending on the application. Or similar items to your original from UK suppliers, e.g. Farnell (BBH windings range), given carriage costs from Germany. More info. please! Martin.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It strikes me that you are out of your league. You need a PE to do your engineering. Most jurisdictions require PE's to do engineering when public safety is involved. Certainly that would be the case if the power levels indicated here were involved.
I saw your corrected post. At those levels, the consequences of error are nowhere as great. But depending upon the application, you can still get into serious trouble.
Bill
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Salmon Egg wrote:

In Britain, PE teachers rarely have any engineering background whatsoever! (BIGEYE is with Zen internet or btinternet.com, "bt" being British Telecom...) Martin.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
BIGEYE wrote:

Does it really? I didn't see a schematic and the document is in German, so I don't trust my translation.
If the 2 two 115V windings are independent, then the answer is (probably) yes. If the windings are tied together internally, then no.

Yes.
But if you do parallel them, I'd knock about 10% off the rating to allow for circulating currents due to turns ratio mismatch until the vendor tells you otherwise.

--
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
------------------------------------------------------------------
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

In other words, one output may be slightly higher than the other, so when put in parallel, you would get some current, which would use up power and becomes heat. For this reason, it is better to get a transformer with the power you need and not put the outputs in parallel.
Also make sure 2 x 115 V means there are two sets of 115V output (4 pins), and not 230V with a center tap (3 pins). In the later case, you cannot parallel the two 115V outputs. And make sure you parallel them in phase.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
john wrote:

You might like to consider the situation where the one end of the two 115v secondary windings in parallel is commoned with one of the 230v primary terminals and the output taken between the other terminals of the primary and secondary windings.
The relative efficiency of doing that, rather than simply taking the output from the parallel secondary windings - I leave to those engineers that really understand transformer operation..
-- Sue
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
| The STEU 320/23 transformer shown here: | http://www.block-trafo.de/fileadmin/productpdf/STEU.pdf | | is 320 kVA. As the transformer has 2 x 115 Volt outputs, can anyone tell me | if the 320 kVA rating is 160 kVA for each output.
This much is certain. The rating of each of the two 115V secondary windings is half of the total transformer rating.
| If this is so, and I need 320 kVA, can I parallel up the two secondary | outputs. Also, would you normally earth down one side of the secondary.
If there are 4 separate terminals, you most likely can. I could not find any wiring diagrams on the web site that would give some certainty to this answer. But in general, if the transformer has 2 secondary windings with the same voltage and current rating, they would be designed to be wired in parallel or series. Since the primary is 230V, the only uses for a 230V series connection would be to get 230V isolated, or as a 460V autotransformer. If that were all it was designed for, one 230V winding would do the job. There's little point in making a transformer with 4 secondary terminals for 2x115V unless they can be wired in parallel (same turns ratio) or in series.
There is still the small chance they didn't do that. You need to find out from the manufacturer just what the wiring truly is (e.g. fully separate secondary windings with exactly the same number of turns).
I've looked at a number of US transformer manufacturers, and many do show their winding diagrams, and some even show application wiring examples.
--
|WARNING: Due to extreme spam, googlegroups.com is blocked. Due to ignorance |
| by the abuse department, bellsouth.net is blocked. If you post to |
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.