Definitions for "Three-Phase"
A generator or circuit delivering these voltages that are one third of a cycle apart in reaching their maximum value.
The three-phase system is a very efficient way of distributing electric power, and is widely used in the power industry. As well as minimising transmission losses, it has the big advantage that it allows the use of induction motors, which are very simple and compact. There are two big problems with using three-phase distribution on railways: the most obvious is the need for two overhead wires, which makes things very complicated; a more subtle problem is that induction motors run at a fixed speed depending on the frequency of the supply current. Italy is the only country where the system was used on a large scale for main lines. It continues to be used on some mountain railways (e.g the Jungfraubahn and Gornergratbahn in Switzerland), where fixed speed is not a problem, and there are few points and crossings to complicate the overhead wires. Nowadays, many locomotives contain electronic inverters which convert DC or single-phase AC into variable-frequency three-phase to allow them to use induction motors without these disadvantages. In Rail3D, you can specify the ThreePhase parameter in OHLE masts to get twin wires.
A power system with three primary voltage waveforms spaced equally (in time) out of phase with each other.
Keywords:  threshold, feeling
Threshold Threshold of Feeling
A type of AC power where three AC currents are introduced at 120° variances.
The most common way of generating and distributing AC electricity