EEVblog Electronics Community Forum
Electronics => Projects, Designs, and Technical Stuff => Topic started by: woodchips on April 03, 2020, 11:15:24 am
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Apologies to all those who find some flat bits of steel and copper windings to be oh so ancient and boring.
Needed a large transformer and bought several three phase ones to play with.
Each transformer is a standard three limb three phase type, each limb is identical with a 230V primary and a 14V secondary. The primaries are connected in Wye to give a 400V 3ph 50Hz input. Similarly the secondaries are connected in Wye to give a 24V 3ph output.
All windings have been isolated so no connection between any of them. All testing done with no load.
One primary on an outside limb connected to 230V supply. What voltages would you expect to see across the other five windings? Why?
Two primaries, one on an outside limb, one on the centre limb, are connected in parallel to 230V with the winding phasing such that the magnetic flux from each winding is adding, so in series. What voltages would you expect to see across the other four windings? Why?
As previous connection except that the primaries are the ones on the two outer limbs. What voltages would you expect to see across the other four windings? Why?
Have a think!
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What's the point of double posting this here, especially when you don't offer the measured levels, or do any more supplementary tests to extend on what you did last week (or whenever it was on another forum).
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Well, since the flux generated by the driven winding is divided in two, the other legs each get half. Since the voltage on a winding is a function of dFlux/dt, the other primary windings will develop about half the voltage of the driven winding. The secondary windings will develop a voltage that is proportional to the voltage on the primary winding they share a leg with.
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Have I double posted it here? Where?
Yes, as duak says, my conclusion was similar that there are two opposing fluxes in the third limb which cancel out.
I just wonder if this was an exam question what the answers would be, whilst very basic, does anyone actually get taught the basics no or is is all on the internet?