Re: 3 phase distribution transformer question

["D&M's High Voltage" <dmshv.davmckin-at-gte-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Gavin,

Check on the high side to see if it is a Delta or a Wye
connection - with the info given it could go either way.
The low side is a Wye connection.

Use the center coil of the transformer.  Disconnect all
connections from the transformer.  To test it, connect
110V to the high side (11KV side).  Read the output
voltage on the low side.  It should read around 2.4 volts
(I'm guesstimating that it is a Delta connection on the
high side).  If it is a Wye connection on the high side,
you'll read about 4.15 volts. Assuming the Delta conn.
you won't have to derate the high voltage by Sqrt 3 (11KV
with 240V input).  The KVA in this config. will be 5 KVA
(regardless whether it is a Delta or Wye connection), but
the actual KVA throughput will be determined by your
ballast arrangement.  Using the center coil will balance the
magnetizing currents between the outer legs - acts just like
a single phase shell type construction.  Good catch!

David L. McKinnon
D&M's High Voltage
P.O. Box 24002
Tampa, FL  33623
(813) 784-8165

E-mail:  DMsHV.DavMcKin-at-gte-dot-net
Webpage:  http://home-dot-netcom-dot-com/~davmckin/DMsIndex.htm



> Original poster: ghub005-at-xtra.co.nz 
> 
> I have been offered a three phase 15kVA, 11kV, 240/415 volt 
> distribution transformer - free if picked up.
> 
> What would happen if this unit was run on single phase 240V? Apart 
> from derating the output voltage by sqrt(3), can a three phase core 
> cope without all of the separate magnetising currents?
> 
> I would appreciate any information or hearing about the experiences 
> that others have had with single phase operation of three phase 
> transformers.
> 
> Safe coiling,
> 
> Gavin Hubbard