The difference between single-phase transformers and three-phase transformers

The main difference between the two is that they are adapted to different types of power supply and communication phases. The single-Phase Transformer is suitable for single-phase AC systems and supplies power to single-phase loads. 。 Three-phase transformers are the mainstream in the power system, suitable for three-phase AC power grids, providing power for three-phase loads while also accommodating single-phase loads. There are differences in structure, capacity, efficiency, and industrial applications between the two types. Three-phase transformers are the core of power transmission and distribution, as well as industrial production. Single-phase transformers are mainly used for power supply to civilian and small equipment.
1.From the perspective of phase number and power supply system: A single-phase transformer is suitable for single-phase AC power grids and can only handle one phase of electrical energy. And in a three-phase AC power grid, it simultaneously handles three-phase electrical energy, and the three-phase magnetic circuits are mutually coupled.
2.Application scenarios: Single-phase is suitable for residential power supply; three-phase is suitable for industrial production, power grid transmission and distribution, large-scale buildings, etc.
3.Structural features: The single-phase cores are mostly of shell type or heart type. Only one set of primary winding and one set of secondary winding are used, resulting in a simple structure. The three-phase core is mainly of the heart-type structure. It consists of 3 primary windings and 3 secondary windings. The structure is relatively complex.
4.Rated capacity：The single-phase capacity is relatively small, mostly in kVA level (ranging from a few kVA to several hundred kVA), and there are no extremely large capacity specifications.    Three-phase capacity covers a wide range and can be made large, ranging from several hundred kVA to tens of thousands of MVA, and it is the only choice for large-capacity power supply in the power system.
5.Voltage level: Single-phase is mainly low voltage (220V/110V, 380V/220V), with almost no high-voltage specifications. Three-phase covers both high and low voltages, with low voltage being 380/220V, and medium and high voltages being 10kV/35kV/110kV/220kV, etc. It is suitable for all stages of power grid transmission and distribution.
6.Efficiency and Losses ：At the same power level, the efficiency is slightly lower and the loss is relatively higher. There is no energy-saving advantage from the coupling of the three-phase magnetic circuit. The three-phase winding magnetic circuits are complementary, resulting in higher efficiency, lower unit capacity loss, and more obvious energy-saving advantages at large capacities.
7.Connection method: Single-phase with simple wiring, the primary and secondary windings are directly wound, only the input/output terminals need to be distinguished. Three-phase has standard connection methods, the core is the star (Y) and triangle (△) configurations, common combinations include Y/Y₀, Y/△, and △/Y (suitable for different voltage conversion and neutral point requirements).
8.Cost and Floor Space：The manufacturing cost of a single-phase single unit is low; if three units are combined to form a "three-phase transformer set" to supply three-phase loads, the total floor space is large, the cost is high, and the cost performance is low. A single three-phase unit can supply three-phase loads, with a low unit capacity cost and small floor space, making it an economical choice for three-phase power supply.
9.Scope of application: Single-phase, solely serving small-capacity civilian loads. Three-phase grid core main equipment, covering all aspects from power generation, transmission, power distribution and transformation to industrial power supply, it is a core device throughout the entire process.