Urban lighting variable power supply - has tapping auto-transformer connected between one phase line and neutral line via injector transformer

摘要

The variable three phase supply is for urban lighting where maximum power is not always necessary such that running costs are minimised. The supplied power level can be varied from 50% to 100% of maximum and can accommodate both high pressure mercury and sodium lamps. Alteration in lighting level is by a single variable tapping (C) auto-transformer (ATVe connected between one phase line(P3) and the neutral (N) via an injection transformer (Ti). Lamps (L1, L2) are connected between the remaining two phases and neutral, or a three phase transformer and a multi-tapped autotransformer can be included to allow connection of further lamps.