On 06/07/2019 23:24, Harry Bloomfield wrote:
Tim+ expressed precisely :
Today we rode a train with two overhead wires but no resistor banks.
This train apparently runs on a three phase supply. Presumably the
rails supplied the third "leg" of the supply but how safe is this with
AC? Wouldn't the rails be dangerously live relative to earth?

It could have been single phase and neutral on the wires, or two phases
and an earth via the earthed rail.

It is three phase and the rail is one phase and is earthed.

Phases are only phased with respect to each other, they dont care about
their relationship with 'earth'.

Voltage is not absolute, It is relative, as any bird sitting on a 132KV
line can tell you




The motor would likely be synchronous, driving a worm gear. The drive
would only allow the car to decend limited by the motor's speed.


--
"It is an established fact to 97% confidence limits that left wing
conspirators see right wing conspiracies everywhere"