1.12 What types of pole-changing motors are used?
Dahlander engines
A Dahlander motor is a two-speed motor that offers a 1:2 switching ratio (e.g., 2:4, 4:8, or 6:12). Motors with Dahlander connections are designed for direct mains start and operate on a single voltage. Only one winding is used, allowing for two different terminal configurations in the terminal box for the individual speeds. The two common Dahlander connection configurations are delta/dye star (delta/double star) and star/dye star (star/double star).
Motors with two separate windings
Motors with two separate windings offer the possibility of different speed ratios. Pole-changing motors with two separate windings have different polarities, for example 4/6, 6/8. The following configurations are used for separate windings: Δ/Δ, Υ/Υ, Δ/Υ.
Typical areas of application
| Area of application | Why reverse polarity? | Typical pole-changing stages |
|---|---|---|
| Pumps and fans | Energy-efficient speed settings, adjustment to volume flow | 2/4 pole, 4/8 pole |
| Compressors | Adaptation to power requirements, protection of the drive system | 2–4 poles |
| Conveyor technology / Crane systems | Coarse speed increments for load positioning | 2–6 poles |
| Elevators / Escalators | Smooth movement, reduced current surge during start-up | 2–4 poles |
| Textile machines / machine tools | Adjusting the processing speed | Multi-stage Pole reversal (2–8 poles) |
