The basic types of transformers are three-phase and single-phase.
Three-phase 7-wire transformers, three-phase 3-winding transformers, and transformers for both motive and illumination power are examples of transformers that obtain power and electric light from a single unit.
Replacing two transformers, one three-phase and one single-phase, with one transformer saves space.

(1) A three-phase 7-wire transformer is a transformer that can supply power to a three-phase load (power) and a single-phase load (electric light) simultaneously with a single three-phase transformer.
(2)Three-phase 7-wire transformer is a transformer that can handle three-phase load and three single-phase load circuits in one transformer, and can balance the primary side by equalizing the load of three single-phase load circuits.

Transformers need to be selected according to the primary-side power receiving environment and the secondary-side load conditions, as well as the wiring and number of phases.

For details, please refer to the video.

2023.2.17：FAQ What is three-phase 7-wire transformer for low-voltage power receiving and distribution?