YVerbindung

YVerbindung, also called Y-Verbindung or star connection, is a method of connecting three impedances or windings to a common neutral point, forming a Y shape. In this arrangement each impedance connects between a line conductor and the neutral. It is widely used in three-phase electrical systems, transformers, and electrical machines to provide line-to-neutral voltages and a neutral reference.

In a balanced three-phase system with a Y-connection, the line-to-line voltage VLL is equal to the phase voltage VPH multiplied by the square root of three (VLL = √3 × VPH). The line current IL equals the phase current IP. The neutral current IN is zero for a perfectly balanced load; if the loads are unbalanced, IN equals the vector sum of the phase currents. The neutral node is often solidly grounded to provide a defined reference and a fault-return path.

Compared with Delta connections, a Y-connection lowers the voltage stress on each winding, distributes insulation requirements, and enables a neutral conductor for grounding and single-phase loads. Its main disadvantages include sensitivity to an open or undersized neutral, which can cause substantial voltages to drift among phases in unbalanced conditions.

Applications include distribution transformers with star-connected windings, low- and medium-voltage power distribution networks, and three-phase equipment designed to operate with a grounded neutral. Y connections are also used in impedance networks for testing and measurement setups.

See also: Delta connection; Three-phase electrical system; Transformer connections; Neutral.