A triple-speed electric motor is a three-phase motor that can be basically constructed in two ways: three separate windings or a common winding with a Dahlander. Motor Dahlander is a motor with special winding that can receive two different locks, in order to change the number of poles, thus creating two distinct speeds.
It is of utmost importance that the Dahlander winding be opened in the second case, otherwise, induced currents will arise when the common winding is fed, which will influence the operation of the motor. Therefore, they can not exist. The reason to be avoided is that these motors have exactly the system of a three-phase transformer. Motors with three windings are closed in star to avoid the same problems. If you need the triangle connection, the possibility of interrupting them when not being fed is mandatory.
The three-phase electric motor provides different speeds on the same axis, but constant. Most are for a voltage value only, because the available reclosures generally allow only the change of speeds. The power and current for each rotation are different, varying according to the load, which can be solved by means of a frequency inverter.