8.7 : Δ-Y回路

A balanced delta-to-Y system features a balanced delta-connected source powering a balanced Y-connected load.

In this delta-Y circuit, a positive abc sequence is assumed to express the phase voltages, which also serve as the line voltages of the delta-connected source.

Kirchhoff's voltage law can be applied to a loop in the circuit to derive a relationship between two of the line currents.

Since a positive sequence is assumed, these line currents have a phase difference of 120 degrees, which is used to determine one of them.

The other two line currents are obtained using the positive phase sequence.

The phase currents of the delta-Y circuit are approximately equal to the line currents.

Alternatively, the delta-connected source can be replaced with its equivalent Y-connected source.

The obtained Y-Y circuit is analyzed by considering an equivalent single-phase circuit and determining the three-line currents.

This circuit can also be transformed into a delta-delta system for analysis purposes as delta-connected load is often preferred due to the ease of altering individual loads.