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Re: [Amps] running two 3 phase transformer serie/parallel

To: "TexasRF@aol.com" <TexasRF@aol.com>, aMPS <amps@contesting.com>
Subject: Re: [Amps] running two 3 phase transformer serie/parallel
From: Bill Fuqua <wlfuqu00@uky.edu>
Date: Thu, 27 Oct 2011 10:24:47 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>
    That depends on the impedance of the power source. If it is very low 
this balancing effect would be minimal and there would be
current flow between the secondaries.
    I have a 5kW plasma generator which is identical to the 3kW versions 
except the 3kW has one transformer and the 5kW has
two in parallel.  Obviously the transformers are very well matched.

73
Bill wa4lav


At 04:55 AM 10/27/2011 -0400, you wrote:
>Hi Mike. back feeding from one secondary to the other may not be such a bad
>  thing. That would force the primary voltage division to the two
>transformers to  be exactly what is needed for equal secondary voltages.
>
>The primary current will be the same since they are in series. Secondary
>current would be +/- small amount as dictated by the turns ratio.
>
>Does that make any sense?
>
>My take on this is to hardwire the two transformers (after phase
>confirmation) and standby for sparks
>
>Very interesting application!
>
>73,
>Gerald K5GW
>
>
>
>In a message dated 10/27/2011 3:37:53 A.M. Central Daylight Time,
>mike@tubby.org writes:
>
>Carel,
>
>I think what you were originally suggesting might  work, as long as you
>have access to both sides of each primary  winding.
>
>If you call the phases Red (R), Yellow (Y) and Blue (B) as we  used to in
>the UK, the transformers #1 and #2 and the ends of the windings  A and B,
>then:
>
>Red = R1A [primary] R1B --- R2A  [primary] R2B
>Yellow = Y1A [primary] Y1B --- Y2A  [primary] Y2B
>Blue = B1A [primary] B1B --- B2A  [primary] B2B
>
>each primary is in series and will see  half-voltage.  You still need to
>know if you are to power it in  'star' or 'delta'.
>
>On the output side the easiest (safest) thing to do  would probably be 6
>x diodes, each one a half-wave rectifier and parallel  the DC side going
>in to the smoothing - this way if one of the  transformers provides 5-10V
>more off load than the other it won't back  need another secondary winding.
>
>Alternatively you could use two  three-phase rectifiers and parallel the
>DC sides going in to your  smoothing.
>
>Rectifier arrangements are  here:
>
>http://en.wikipedia.org/wiki/Rectifier
>
>
>Regards
>
>
>Mike  G8TIC
>
>
>
>
>On 26/10/2011 10:40, pc5m, Carel  wrote:
> >
> >
> > Hi Gerald,
> >
> > We have here 400V 3  phase power (voltage between the
> > phase's) and as a result 230V between  a phase and ground. So the lowest
> > voltage I have "available" is  230Vac...
> >
> > gl, Carel.
> >
> > On Tue, 25 Oct
> >  2011 18:02:30 -0400 (EDT), TexasRF@aol.com wrote:
> >
> >> Carel,  what is
> > your primary voltage there? Do you have three phase primary  power?
> >>
> > 73,
> >> Gerald K5GW
> >>
> >>  In a message dated 10/25/2011 1:11:15 P.M.
> > Central Daylight Time,  pc5m@xs4all.nl writes:
> >>> Hi,
> >>>
> >>> I  have
> > two identical 3 phase high voltage transformer (each around 4KVA  /
> >>> 50
> > kg/ 100 pounds). Issue is they are designed for  US 3 phase voltages.
> > (so
> >>> 120 / 204V) so can't use them  in Europe as is. What I would like
> > to do is to
> >>> put the  2 units at the primary side in serie and at the
> > secondary side  in
> >>> parallel. Primary and secondary in wye  config.
> >>>
> >>> Q: Would there be any benefit of  connecting the secondary windings
> > of the
> >>> two  transformers first parallel and than rectify (with only
> > one  rectifier
> >>> bridge) or the other way around ? For me it is  much
> > easier to first rectify
> >>> both transformers and  than put the rectified
> > voltage parallel (only one
> >>>  highvoltage interconnect between both the
> > big/heavy transformer  boxes.).
> >>> I have seen some constellations
> > with two 3  phase transformer to gain some
> >>> benefit in creating
> >  additional phases in order to reduce the ripple voltage
> >>> even  more.
> > Don't know if I could utilize such a thing as well ? However,  if
> >>> I
> > recall they were placed in parallel at the  input.
> >>> Thanks for any
> > idea's . Gl,  Carel
> >>>
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