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Author Topic: Why do Arc-Welders cause the Wheels of old House-Meters, to Spin Backwards ?  (Read 9439 times)

guest1289

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    • The download link for the document containing my 'Inventions and Designs'
Why do Arc-Welders cause the Wheels of old House-Electric-Meters,  to Spin Backwards ?

   There is a video on youtube showing this.

   (  There are also videos on youtube showing  Home-Solar-Panels   causing the  Same-Effect,  but I assume that thats because they are literally putting an excess of power back into the electrical-grid  )

  I think the answer stated for Arc-Welders,  is reactive-power ( the erratic / jolting characteristic of the current resulting from an Arc-Welder  ).
     
   -  Could that possibly be demonstrated with a water-hose connected to a water-meter( a water-meter that can spin backwards ),  and by somehow extremely quickly stopping and starting the water flow,  I doubt it,   since there is actually very little similarity between water-flow and electric-current.
_________

    I had a theory that the open-air-spark from the Arc-Welder was somehow absorbing either  Electromotive_Force(  https://en.wikipedia.org/wiki/Electromotive_force )  and / or  even electrons from the surrounding atmosphere,  in a similar way to how a water-fountain in a closed damp room,  could possibly dry the room when the moisture in the air clings to the flowing-water of the fountain rather that to the walls of the room,    but,  I have no evidence for either of these theories.
     

Bob Smith

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You may find the answer in Don Smith's explanation of what happens when a capacitor discharges, and where the outgoing charge comes from.
Bob

Magluvin

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The first thing to do is see what drives the disk in the meter. Is the disk an armature of an AC motor in the meter? Havnt looked for it yet. But if it moves with AC, then either phase of the AC should cause the wheel to to spin in one direction. So how could it go backwards? ???

Mags

Dog-One

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Probably more than anyone really wants to know, but here's a pretty thorough explanation:

http://www.usbr.gov/power/data/fist/fist3_10/vol3-10.pdf

Best I can tell in answer to the OP is the current/voltage relationship (phase) must be altered far beyond the typical 90 degree lag to get the effect of the disc rotating in the opposite direction.  Meaning the power factor has either gone negative or gone beyond 1.0.  Whether a typical arc welder can do this or not...?   I can't say.  There are probably other factors at play.

This statement within the document exposes it is clearly possible for an electromechanical meter to run backwards:
Quote
3.8.  DETENTS. A detent or ratchet is sometimes attached to meters to prevent rotation in a reverse direction when it is desired not to register reverse power flow. This usually consists of a collar having notches or pins which is placed on the disk shaft and a pawl attached to some fixed part of the meter which engages the notches or pins upon reverse rotation but slides easily over them in the forward direction. The slight amount of friction introduced by the installation of a ratchet may affect the light-load registration and require that the meter be readjusted.

Grumage

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The first thing to do is see what drives the disk in the meter. Is the disk an armature of an AC motor in the meter? Havnt looked for it yet. But if it moves with AC, then either phase of the AC should cause the wheel to to spin in one direction. So how could it go backwards? ???

Mags

Dear Mags.

Go backwards? Yes they can.

I spent nigh on two decades working for my local supply industry, HV distribution. Back then the circuit protection consisted of electromechanical relays. The discs would either rotate and trip the local breaker if the fault was " in zone " or just go hard against the backstop for an out of zone fault. The current transformers were tested during commissioning for polarity by doing " flick " tests, the application of a low current DC pulse either side of the CT. I know this sounds completely crazy but yes , AC has direction!

There was also a gizmo available " black market style " for around £50.00 that you gingerly attached to your meter and sent it zooming backwards.

As I see it, under certain circumstances an Arc welder might just create a current large enough in opposition to the incoming current and this is what is seen. With the phasing out of electromechanical meters being implemented more and more this phenomenon will become the stuff of legend.

Cheers Grum.

gyulasun

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....
As I see it, under certain circumstances an Arc welder might just create a current large enough in opposition to the incoming current and this is what is seen.
....

Yes and as an addition I think that the negative resistance created by the electric arcs (a characteristic in their VI curve) may cause oscillations in the welding transformer and this can transform back to the mains through the primary coil. These oscillations my occasionaly exceed the mains voltage amplitude and behaving as a voltage source overriding the mains incoming amplitude, thus causing the large enough 'backwards' current flow.

Gyula

allcanadian

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@Grumage
Quote
As I see it, under certain circumstances an Arc welder might just create a current large enough in opposition to the incoming current and this is what is seen. With the phasing out of electromechanical meters being implemented more and more this phenomenon will become the stuff of legend.


I would agree, few understand that we are not actually connected to the grid, we are connected to a fairly large line transformer which is connected to the grid. If a large enough disturbance of sufficient quality coupled to the line transformer secondary and the line capacitance then any number of supposedly strange things might occur.


I read of one instance where an induction motor acting as a generator could supposedly generate full power at under 1/4 of the rated RPM. As we know an induction generator uses reactive power from the grid at 60 Hz to energize the stator coils and the armature must be above this frequency to produce a phase differential to generate power. It was theorized the induction generator may have coupled to the line transformer forming an LCL circuit allowing it to operate at a very much lower RPM while still generating full power.


AC

Turbo

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If your wall voltage is 120 V, and you raise the voltage on your side to 200 V then, from the meters perspective, it will look as if the power is running back into the 'grid'.
I say look as if because it's a trick, the power comes from the same source, it's just switched in a different manner(unless you have your own source like solar, of course),there are devices that charge up capacitors in parallel just to discharge them in series back into the source, just to fool the meter.
Of course the same can be achieved with inductive equipment like for example welders.

Magluvin

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If your wall voltage is 120 V, and you raise the voltage on your side to 200 V then, from the meters perspective, it will look as if the power is running back into the 'grid'.
I say look as if because it's a trick, the power comes from the same source, it's just switched in a different manner(unless you have your own source like solar, of course),there are devices that charge up capacitors in parallel just to discharge them in series back into the source, just to fool the meter.
Of course the same can be achieved with inductive equipment like for example welders.

Just seems odd. If one phase of AC is pushing current in and the other phase pulling current out, and the meter flows the same direction for each, how would the wheel determine whether current is going in or out in order to reverse direction?

Going to read the pdf

Mag

minnie

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   YouTube "Three phase meter running backwards".

Grumage

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   YouTube "Three phase meter running backwards".

Dear minnie.

Did you forget the link?  :)

Cheers Grum.

minnie

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  Just a bit beyond my capability to do a link!
           John.


minnie

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   Yes,that's the one. Rotten luck for me is that they've changed our meters
  to sort of digital thingies!!
          John.p