Hi all,
I have recently been working on replacing a defective 690v 3 Phase induction motor driving a cooling fan,when i inspected the name plate it has a star configuration for slow speed and a star star configuraton for high speed.The motor has six terminal terminations (not including earth conductors).
When looking at the wiring configuration to the fan its as follows;
slow speed terminals 1,2 and 3 are used for 3 phase electrical supply.
High speed consists of the supply for 1,2 and 3 being disconnected from the incomming supply and then all joined together via little jumper loops in a contactor,terminals 4,5 and 6 then supplies the motor.

Has anyone ever heard or worked with such a configuration?Does this configuration just double up the three phase field windings in star (like the name suggests), producing more electromagnetic force for the stator to react upon?

Where i work has the same wiring set up for other motors and pumps,any help on this matter would much appreciated!

James