Quote:
Originally Posted by Lucien Nunes
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A historical note about egregious dumping of DC into the mains: One of the first attempts in the UK at a fully electronic theatre-lighting dimmer was Strand's 1949 thyratron-based unit that came to be known as 'Woody's Electronic' after J.T.Wood, its designer. Probably to sidestep a patent by Century in the USA who were working towards a similar goal, Wood started out by using three thyratrons per channel, one on each phase, to provide controlled 3-pulse rectification feeding variable voltage DC to the lamps. The entire current used by the installation was DC and the sum of the three line currents, totalling some hundreds of amps of DC, returned via the neutral! Not surprisingly, one of the first installations to be conmissioned (possibly Reykjavik Opera House) resulted in the neutral of the theatre's main supply cable burning out. It had other problems including thyratrons running away, so the company soon returned to electromechanical dimmers pending the arrival of thyristors.
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They did a range of saturable reactor control systems as well in the '50s and early '60s before thyristors took over. Oddly enough, the
only type of theatrical dimmer system where I ever got my hands on the inner workings.