Unipolar switching power supply means that the output is unipolar, that is, there are only positive and negative outputs. Compared with bipolar switching power supply, bipolar switching power supply has three outputs, which are divided into positive power supply, negative power supply and ground wire.

Single-phase transformers have simple structure, small size and low losses, mainly small iron losses, and are suitable for application and promotion in low-voltage distribution networks with low load density. Some people believe that single-phase power supply has the magic of "loss reduction", that single-phase transformers are more energy-saving than three-phase transformers, and that single-phase power supply systems are superior to three-phase power supply systems. In fact, it is not the case. Single-phase transformer and single-phase power supply system are only supplementary forms of the current three-phase power supply system. Due to the constraints of its own characteristics, it can only be used in certain specific fields.