Three-phase transformers are widely used in power systems to step up or step down the voltage levels in three-phase circuits. The connection of the three-phase transformer windings determines the output voltage and current characteristics of the transformer. There are several types of connection groups for three-phase transformers, each with different advantages and disadvantages.

The three most common connection groups for three-phase transformers are Y-Y, Delta-Delta, and Y-Delta. The Y-Y connection group consists of three windings connected in a Y configuration on both the primary and secondary sides. This connection group provides a neutral point on both the primary and secondary sides, which can be used for grounding and for connecting single-phase loads. The Delta-Delta connection group consists of three windings connected in a Delta configuration on both the primary and secondary sides. This connection group does not provide a neutral point and is primarily used in applications where a neutral connection is not required. The Y-Delta connection group consists of three windings connected in a Y configuration on the primary side and in a Delta configuration on the secondary side. This connection group provides a neutral point on the primary side and is commonly used in applications where a neutral connection is required on the primary side, such as in distribution systems.

Each connection group has its advantages and disadvantages. The Y-Y connection group provides excellent phase-to-phase and phase-to-ground voltage regulation, but its current rating is limited due to the small winding wire size required for the high number of turns in each winding. The Delta-Delta connection group can handle higher current ratings than the Y-Y connection group due to the larger wire size, but its voltage regulation is not as good. The Y-Delta connection group provides good voltage regulation and can handle high current ratings, but it is more expensive than the Y-Y and Delta-Delta connection groups due to the additional winding required.

In conclusion, the selection of the connection group for a three-phase transformer depends on the specific application requirements, such as the required voltage regulation, current rating, and cost.

LuShan, est. 1975,  is a Chinese professional manufacturer specializing in power transformers and reactors for 48 years. Leading products are single-phase transformer, three-phase transformers, DC inductors, AC reactors, filtering reactor, expoxy resin high-voltage transformer and intermediate, high-frequency products. Our transformers and reactors are widely used in 10 application areas: rapid transit, construction machinery, renewable energy, intelligent manufacturing, medical equipment, coal mine explosion prevention , excitation system, vacuum sintering, central air conditioning.

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