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Re: NEON- Building a loading meter
I'm sending this a second time, 24hrs and I still haven't seen the first
posting. If duplicated, sorry. Steve
Steve wrote:
>
> Building a home-brew meter though economically practical, is not really
> practical from the stand point of just how important this tool is. As boon.
> stated 80 - 90 % of all transformer failures are caused by improper loading.
> Though we transformer manufactures keep on replacing these units there is
> definately a large cost associated with actually replacing them in the field.
>
> With the importance of proper loading associated with the ecalating costs of
> labor doesn't it make sense that we purchase equipment with some relative
> value. The meter I use in the feild is far from the best equipment for the
> job, but from a trully practical standpoint I think it is suitable and well
> within the average signguys/gals budget.
>
> What I use and recommend is the Fluke Model 87 Multi-meter with an 80K-40 HV
> probe, the combined value is aprox. $400.00us when shopped around. The nice
> thing about owning a meter of this quality is that not only does it
> function as a mA meter and HV meter but you can use it for numerous other
> functions and not for just loading your trans.(PRIMARY VAC)
>
> As far as which method mA or HV is the more accurate means of loading, we
> have found that if you strictly depend on current(mA)you are apt to get
> readings that are adversly effected by the reactance in your secondary
> wiring, and will be prone to overload.
>
> Using the HV method is a much easier test to actually take (parrallel as
> apposed to series), it also takes into account voltage that is lost to ground
> via capacitive coupling which adds to the actual load on the trans. but is
> not taken into consideration on a mA test.
>
> Dirk talks about "G-Factor" though I have never heard it called this, the .5
> maximum operating voltage is accurate. In other words, 15,000 volt trans. hs
> an OCV of 15KV or 7,500 per side. Once the arc is struck in the tube a
> properly loaded trans. should ballast down to aproximately 1/2 the plate or
> OCV. 7,500 or 3,750 per side.
>
> Another nice thing about loading by voltage is that not only do you learn
> where you are, but the reading will actually tell you exactly what trans. to
> use. e.g. You have a 9000/30 and you are getting readings of 2700 vac per
> side. 2700 x 2= 5400 total operating voltage divided by .5 (g-factor) = 10800
> volt Optimum OCV (open circuit voltage). So the logical choice in this case
> would be a 12000/30 (in the US).
>
> Now the best of both worlds is performing both tests.
>
> Online Physicists, please offer your opinion as to the potential pitfalls to
> this method (if any) and please define G-Factor and mabey bare it's origin.
>
> Steve