04-01-2018, 01:05 PM
(04-01-2018, 03:42 AM)Synchrodyne Wrote: I have heard various “stories”, ranging from their being outright illegal to their being frowned upon by electricity distribution authorities because they put DC back on to the mains. Conceivably individual electricity distribution authorities had the power to ban live chassis equipment if they so chose.
It's not a consequence of 'live chassis' though in practice they often go together, live chassis and half-wave rectification.
But more recent equipment - TV's using switch-mode power supplies - may well use full-wave rectification direct from mains, chopper-regulated, supplying the rest of the circuitry without isolation. Admittedly, these will be built on a printed-circuit board and the supporting metalwork (as near a chassis as we'll get) could be either isolated, earthed, or connected to 0V line, which whizzes up and down according to the input bridge rectifier. Yet such a set would not have any DC component in its input current waveform.
The safety aspects of 'live chassis' are well known, of course, and it would be interesting to hear if Australia and NZ steered away from them in favour of the more expensive isolating transformer on safety grounds!
But what about DC installations - or were there none? Or did they adopt the American practice of isolated/earthed chassis with a live busbar?
