It was done on large three phase motors on radars which tended to have to be
tested with covers off, and it was most certainly earthed on one rail.
Brian

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"Vir Campestris" wrote in message
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On 06/07/2019 21:08, The Natural Philosopher wrote:
Why would they be? If the rails were earthed...

a three phase supply doesnt have to have each limb symmetrical with
respect to earth.

Consider a star or delta transformer with one phase earthed.

I just spent ten minutes trying to check you out - and failed. I can't
find anything saying that in either English or French.

One of the few other such systems is the Jungfraubahn, which I went on a
couple of years ago. I'm damn sure there isn't a live rail - I walked
across the track - so your guess must be correct.

Or you have a source I couldn't find!

Andy