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Six phase electric supply.

Sparkingchip
db3fecfec837110019a09ec7585f1e33-huge-a72a8449-52a6-4c2f-b7dd-13b18ecd4933.jpg


This photo has appeared on my Facebook page.


I will let this run a bit then tell you where it is and who posted if if no one guesses, though I suspect at least one forum member will recognise it straightaway.


If I read it correctly it does say it has a six phase supply.


Andy Betteridge
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  • 0
    The modern way to make 6 phases, for a 12 diode rectifier, is to have one 3phase transformer core and primary, and 2 sets of 3 secondary windings, one secondary configured as a delta, and the other 3 configured as a star, with the no's  of turns in the right ratio to give the same p-p voltage on all 6 lines - the advantage is that the DC that is produced by rectifying this with  12 diode bridge is almost ripple free, even without any smoothing capacitance, and when loaded  the primary side currents are not dominated by 3rd harmonics, and has a very good power factor compared to a simple rectifier.

    The technique dates back to the late 1800s, and DC for traction current for trains and trams was often derived this way.

    670V may be ex  London underground.

    I thought Kempton Park was 200-250V, is that recollection wrong  ?



    It is still done today though the diodes are now chunks of silicon (or at least several in series to withstand the reverse voltages ), to derive DC supplies for large valve based broadcast transmitters.
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  • 0
    The modern way to make 6 phases, for a 12 diode rectifier, is to have one 3phase transformer core and primary, and 2 sets of 3 secondary windings, one secondary configured as a delta, and the other 3 configured as a star, with the no's  of turns in the right ratio to give the same p-p voltage on all 6 lines - the advantage is that the DC that is produced by rectifying this with  12 diode bridge is almost ripple free, even without any smoothing capacitance, and when loaded  the primary side currents are not dominated by 3rd harmonics, and has a very good power factor compared to a simple rectifier.

    The technique dates back to the late 1800s, and DC for traction current for trains and trams was often derived this way.

    670V may be ex  London underground.

    I thought Kempton Park was 200-250V, is that recollection wrong  ?



    It is still done today though the diodes are now chunks of silicon (or at least several in series to withstand the reverse voltages ), to derive DC supplies for large valve based broadcast transmitters.
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