Dahlander winding: Does the voltage rating change between connections?
Two-speed motors can be designed to be rated for constant torque, constant power or variable torque. A constant-torque motor would be selected for a load like a conveyor that requires the same torque to drive the load at any speed. The power would be higher for the high speed connection since power is torque multiplied by speed. A constant-power motor would be used for something like a drill press that is operated at higher speed and lower torque when a smaller diameter bit is selected. A variable-torque motor would be used for a load like a fan or centrifugal pump that requires more torque to operate at a higher speed.

A motor could be designed for both two speeds and two voltages, but that would be more complicated and require more connection terminals. It would also be possible that some of the two-speed designs may be operable at more than one voltage without adding connection options, but only operating at one speed and not necessarily at the original torque or power ratings.

Three-phase induction motors can have a lot of different design configurations. Only the most popular configurations are catalog or stock items. Many special configurations are described in texts and handbooks, but there are configurations manufactured that are rarely seen or even one-of-a-kind.