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Mercury Arc Rectifier #2


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The basic 3Ph waveform




The waveform from the transformer shown above is the normal 3Ph waveform superimposed with a second opposing waveform at 180° giving six peaks per cycle.




As the MAR only uses the negative half of the waveform we can chuck the positive side out.





The cathode only takes current from the highest negatively charged anode giving a rippled DC output. Fine for most applications and I will say far better than some of the modern rectifier sets I’ve put in.




Looks like the village fete is about to start Guinness






Electroplating requires a very smooth DC output smoother than a six arm unit can provide, a 12 arm bulb as in the first picture would be better but not an exactly brilliant DC output.


The transformer secondary gets interesting with two opposing groups of two sharing the same phase angle













Using multiple MAR bulbs and multi turn transformers up to 96 phases can be obtained from a single 3Ph input to supply an almost ripple free DC output. These would only be small units used for (expensive) high quality electroplating.



This is a 48Ph unit derived from 3Ph.





© Tony S


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