Single-phase transformer that the primary winding and secondary winding are single-phase winding transformer, also includes single-phase pole mounted transformer, such as 11kv 230v single phase transformer, 11kv 240v single phase transformer, 12 kva transformer. simple structure, small volume, low loss, mainly iron loss is small, suitable for the application and promotion of low voltage distribution network with small load density. Simple structure, small size, low loss, mainly small iron loss, suitable for application and promotion in low voltage distribution network with small load density. Some people therefore think that single-phase power supply has the magic power of 'loss reduction', that single-phase transformers are more energy-efficient than three-phase transformers, and that single-phase power supply system is more superior than three-phase power supply system. In fact, single-phase transformers and single-phase power supply system is only the current three-phase power supply system in the form of complementary, because of its own characteristics of the constraints, it can only be applied to some specific areas.
Transformer small capacity of the cost of light load areas for the construction of single-phase power supply system can reduce the construction investment. Large load areas for single-phase power supply system transformation, there must be a large economic investment. Some single-phase transformers in residential areas of the pilot, the implementation of a large transformer into a number of small transformers, near the load installation, shorten the distance of the low-voltage trunk line, as the power point to the load distance is certain, shorten the distance of low-voltage power supply, will inevitably have to prolong the distance of the high-voltage power transmission, such transformation requires a large amount of investment. In order to reduce the line loss of the low-voltage trunk line, the high-voltage line into the load centre, increase the investment in high-voltage line construction, the use of multiple small-capacity transformers after no-load loss and load loss, than the original single large-capacity transformer more.