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Posted by RoyJ on July 13, 2008, 8:18 pm
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You need to understand that Karl has a single phase (NOT 3phase!!!) 240
volt submersible pump where the run cap is topside. So the currents are
measured between leads that are normally buried inside the motor. The
currents he is quoting come directly from the manufacturer's service
literature.
Robert Swinney wrote:
> Roy J sez:
>
> "I don't have my book at home to figure it out but, explain to me why the
imbalance, I'm curious"
>
> If I might take a stab at it, my W.A.G. is:
>
> Karl, like so many who build RPCs, probably lost sight of the need to properly
balance the
> idler-motor / load network. They throw in a few random-valued capacitors and
step back to admire
> their work, giving no thought to completing the job in anything resembling
good electrical design.
> They seem totally thrilled their RPC will start and run and assume that is
good enough.
>
> In all likelihood the currents are measured with a "clamp-on" type of ammeter.
In that process true
> currents are not being measured among wildly different phase relationships in
the 3 leads of an
> unbalanced RPC.
>
> IMO, guys like Karl would do well to build proper RPCs before asking questions
on RCM about wire
> sizing for bogus currents. People like Bruce with electrical backgrounds
would be better able to
> give meaningful advice re. wire sizing if they had any notion of what the
3-phase currents in
> question were all about. It is impossible, as far as I know, to accurately
measure unbalanced
> 3-phase currents with an clamp-on ammeter.
>
> Bob Swinney
>
>
>
> ** Posted from http://www.teranews.com **
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>
> "I don't have my book at home to figure it out but, explain to me why the