Tesla,

As I discussed many years ago, the decision for the US to standardise on 120V was the penalty for being first in the game and the numbers were such that to adopt a higher domestic voltage was thwarted by the quantity of those already supplied. A tension of 240V was always part of the supply equation even in the US – grounded centre tapped – and this was replicated in the limited 120-0-120V DC municipal supplies in the UK that were available until the 1940’s.

In Europe the advantages of a higher supply voltage were able to be rolled out to their customer base - because it was smaller at the time. In the UK a 240V line to ground, 3-phase, was standardized with the delivery of AC power. In continental Europe, 3-phase 127V line to ground systems were the initially norm (230V phase to phase).

The colours are a hang-over of various national systems. In the UK pre 1970’s the domestic wiring colours were red (phase), black (neutral {grounded in US}), and solid green (earth{grounding in US}). Other European countries had other systems – in the German-speaking world, red was earth (Grounded)!! Imagine that for cross-border co-operation!

The colours were changed to the present because a significant proportion of the male population is red-green colour blind and this had a Darwinian effect on those UK electricians and their customers. Brown, blue and yellow/green wiring can be distinguished by most members of the population – it has absolutely nothing to do with protectionism.

All UK railroad signalling equipment is 110V – a hangover from when Westinghouse (USA) first supplied most of the world’s railway electronic signalling equipment. My spare US domestic stuff now sits with my local tourist railway where I volunteer my services at a weekend.

As for the frequency – I have heard it said that Tesla (your namesake) adopted 60Hz by experiment in the local city supply environment. Europe was always (post-Napoleon) driven by metrication and 50Hz, thus comprised 100 phase peaks per second – i.e. nicely metric.

But meanwhile, back to kitchen stuff …

Last edited by Hutch; 05/05/15 05:52 PM.