1.1.11 How does the Dahlander connection work in a pole-changing motor?

The Dahlander connection uses a special circuit for switching between slower speeds (delta connection) and higher speeds (double star connection). At low speeds, the connection resembles a delta, while at high speeds it resembles a double star. It is therefore also referred to as a delta-double star connection. The speed changeover is achieved by changing the poles at a ratio of 2:1. In pole-changing motors, the delta connection is established by connecting the mains terminals (L1, L2, and L3). The double star connection is achieved by bridging terminals 1U, 1V, and 1W and connecting the mains terminals (L1, L2, and L3) to terminals 2U, 2V, and 2W.