[RE-wrenches] Preventing 24/7 Transformer Losses

[William Miller]

Garrison:

 

Are you sure you need a transformer to connect directly to the 3 phase?  I
believe the system you refer to is an open-delta.  We've installed the old
SB2500 units on open-delta before.  This was before the neutral sensing
requirements, however.  Many inverters have provisions for disabling the
neutral sense, if that would help.  I'd verify there is actually a need for
a transformer.

 

William

 

PS:  I do remember that I incorrectly ordered 208 inverters for the
open-delta installation referred to above.  It was actually a 240 volt three
phase.  The SB2500s had to be specified for the correct voltage.  I had to
eat a lot of freight to get 5 inverters reconfigured..

 

Wm

 

 

Gradient Cap_mini
Lic 773985
 <http://www.millersolar.com/> millersolar.com
805-438-5600

 

From: RE-wrenches [mailto:re-wrenches-bounces at lists.re-wrenches.org] On
Behalf Of Garrison Riegel
Sent: Friday, November 14, 2014 7:51 AM
To: re-wrenches at lists.re-wrenches.org
Subject: [RE-wrenches] Preventing 24/7 Transformer Losses

 

Hello Wrenches,

 

In my area we end up installing a lot of systems on 240V 3Ph high leg
services.  To allow for more inverter options (like TL that require a
neutral) it seems like using a transformer would a good idea, but it is hard
to justify the losses under load and especially 24/7 losses required to keep
the core magnetized.

 

In a recent post on this same subject by Greg Smith from SMA he wrote, "If
you specify a transformer specifically for solar PV designs then the losses
are negligible."  The transformer tech people at the manufacturers I spoken
with have no idea what this means.  I emailed Greg for clarification but
have not yet had a reply.  On a recent project that needed a 30KVA
transformer the 24/7 losses were 200-300W depending on manufacturer, which
is not negligible, and in my area would require about 2kW of PV to offset.  

 

Does anyone know what Greg might be referring to?

 

What are folks doing to mitigate these losses?  Some kind of DC actuated
switch on the utility side of the transformer maybe?

 

Anything else to keep in mind when specifying a PV specific transformer?

 

Thank you for your thoughts.

 

Garrison

 

Garrison Riegel

Project Manager |  <http://www.solarserviceinc.com/> Solar Service Inc

[p] 847-677-0950 |  <mailto:garrison at solarserviceinc.com>
garrison at solarserviceinc.com

 

NABCEP Certified PV Installation ProfessionalT

 

 

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