Dahlander pole changing motor

The motor may have fixed or variable torque depending on the stator winding.

In 1897 he invented an electrical configuration to switch between poles in a motor for which he was granted a patent along with his co-worker Karl Arvid Lindström.

[7][8][9] Normally, the electrical configuration of windings is varied from a delta connection (Δ) to a double star connection (YY) configuration in order to change the speed of the motor for constant torque applications, such as the hoists in cranes.

[7][9] Dahlander motors have advantages compared to other speed control systems like variable frequency drives, as there is less power loss.

However, the Dahlander motor has the disadvantage of fast mechanical wear and tear due to changing speeds in such a drastic ratio; this type of connection also produces high harmonic distortion during the shifting of poles as the angular distance between the power generated increases as the poles are decreased in the motor.