The difference between a three-phase transformer and a transformer group consisting of three single-phase transformers

Three-phase transformers are suitable when there are three-phase motors and equipment at the load end.； If there are three single-phase transformers, the load end cannot be connected to three-phase motors and equipment, but can only be connected to single-phase electrical equipment.

Not necessarily, it depends on the specific application conditions! For example, the rectifier transformer of a large AC drive uses three mutually isolated rectifier transformers to supply power to each phase of the motor separately!

Carbide furnace transformers are divided into single-phase and three-phase

There are many differences. In terms of performance, the main differences are as follows:: 1. Transformer impedance is different ； 2. Transformer losses are greater ； 3. The three-phase balance of three single-phase transformers is better than that of three-phase transformers (caused by the different three-phase magnetic circuits of three-phase transformers) ； 4. Better heat dissipation, but takes up more space ； 5. High reliability and easy to repair and replace. 6. The cost of three single-phase transformers is about 50% higher than that of one three-phase transformer. According to general analysis, three identical single-phase transformers with primary and secondary side windings are connected in a symmetrical three-phase manner to form a three-phase transformer group. The magnetic circuits of each phase of this transformer group are independent of each other. When a three-phase symmetrical sinusoidal voltage is applied to the primary side, the main magnetic flux ΦA/ΦB/ΦC of the three-phase winding is also symmetrical. The three-phase no-load current is also symmetrical. In places where extra-large capacity transformers/transportation conditions are restricted, this transformer set can be used to facilitate transportation/reduce spare capacity. The core of the three-phase core transformer is evolved by combining the cores of three single-phase transformers. In order to simplify the structure, facilitate manufacturing, reduce volume, and save materials, the center lines of the three-phase core columns are usually arranged in the same plane, evolving into a commonly used three-phase core transformer core. In this core structure, the magnetic resistance of the two-phase magnetic circuit on both sides is larger than the magnetic resistance of the middle phase. When the applied three-phase voltage is symmetrical, the magnetic flux of each phase is equal, but the no-load current of the three phases is not equal, and the no-load current of the middle phase is smaller. The performance is more obvious in small-capacity transformers. Generally, I0A=I0C=(I.2-1.5)I0B. In large-scale transformers, the imbalance is small. Compare: The three-phase cores of the group transformer are independent of each other, the three-phase magnetic circuits are not related, the three-phase magnetic circuits are symmetrical, and the three-phase currents are balanced, which is easy to disassemble and transport, and can reduce the spare capacity. The cores of core-type transformers are not independent of each other, and the three-phase magnetic circuits are interrelated. ； The magnetic circuit of the intermediate phase is short, the magnetic resistance is small, and the excitation current is unbalanced, but its impact on the actual operating transformer is minimal. Under the same SN, core-type transformers are economical/material-saving/small in size/weight. The wiring methods and connection limit groups of core-type transformers are:: Star/angle, star/star, angle/angle, angle/star, 12 groups, 48 ​​wiring methods. There are only two types of connection groups for single-phase transformers: I,i0/I,i6

There are several main aspects, each with different pros and cons: 1. Different costs; 2. Different wiring groups; 3. Different load rates; 4. Except for special transformers, there are very few "single-phase" ones (two-phase instead of single-phase). For example, the boiler's electric precipitator, electric refining, and electric desalination transformers are all two-phase. 5. There are also problems with the maintenance of single-phase transformers. For example, whether the high-voltage side of the three transformers forms a Y shape or a △, etc. There are too many requirements. Single-phase transformers are not recommended except for special occasions.