{"id":58254,"date":"2025-04-08T09:20:45","date_gmt":"2025-04-08T07:20:45","guid":{"rendered":"https:\/\/lcsn2025.dev-labaleine.fr\/?p=58254"},"modified":"2026-09-15T15:32:52","modified_gmt":"2026-09-15T13:32:52","slug":"three-phase-transformer-connection-types","status":"publish","type":"post","link":"https:\/\/www.lecosinus.fr\/en\/les-differents-types-de-couplages-dun-transformateur-electrique-triphase\/","title":{"rendered":"The different types of couplings of a three-phase electrical transformer?"},"content":{"rendered":"

Les transformateurs \u00e9lectriques occupent une place essentielle dans la transmission et la distribution de l’\u00e9nergie. En isolant \u00e9lectriquement les r\u00e9seaux et en adaptant les niveaux de tension<\/a> pour r\u00e9pondre aux besoins sp\u00e9cifiques des applications, ils assurent un transfert efficace et s\u00fbr de l\u2019\u00e9nergie \u00e9lectrique. Par ailleurs, la configuration des enroulements, c\u2019est-\u00e0-dire la mani\u00e8re dont les bobines du transformateur sont interconnect\u00e9es entre elles permet de r\u00e9pondre \u00e0 diff\u00e9rents besoins des installations \u00e9lectriques.\u202f\u00a0<\/p>\n\n\n\n

\"Diagram<\/figure>\n\n\n\n

Star coupling (Y)<\/h2>\n\n\n\n

In this configuration, each winding is connected between a phase and a common point called neutral. This coupling is particularly suitable for high-voltage applications, as it reduces the voltage across the windings by a factor of \u221a3, thus reducing the insulation risks. <\/p>\n\n\n\n

But its main interest lies in the presence of the neutral point in secondary schools. In this configuration, the neutral allows the transformer to be grounded, the neutral regime to be changed and to avoid the floating of the power grid with respect to the ground, which could damage the following systems (e.g. sensitive digital controls) <\/p>\n\n\n\n

Incidentally, it also allows distribution for single-phase loads between phase and neutral. Be careful in this case to remain vigilant and not to significantly unbalance the transformer. <\/p>\n\n\n\n

Triangle coupling (D or \u0394)<\/h2>\n\n\n\n

Here, the windings are connected end-to-end to form a closed circuit, with no neutral point. This configuration is advantageous for low-voltage applications requiring high currents, as it reduces the current flowing through each winding by a factor of \u221a3. However, the absence of neutral does not allow for grounding. This is why this coupling is generally used in the primary of three-phase transformers<\/a>.<\/p>\n\n\n\n

Zigzag Coupling (Z)<\/h2>\n\n\n\n

Zigzag coupling is a variant of star coupling where each winding is divided into two halves, each connected to different phases. This configuration is used to reduce voltage imbalances and harmonics in distribution networks. <\/p>\n\n\n\n

This configuration is not used much and should be avoided as much as possible because transformers are much larger, complicated to manufacture and therefore expensive. <\/p>\n\n\n\n

Primary and secondary, which couplings to choose? <\/p>\n\n\n\n

In a three-phase transformer it is always preferable to mix the couplings between the primary and the secondary, so you have a partial rebalancing effect of the networks and a limitation of harmonics. <\/p>\n\n\n\n

The most commonly used couplings: <\/p>\n\n\n\n