Making reference to the diagram of Figure 6, the starting modality foresees the initial phase with star-connection of the winding to be realized through the closing of the circuit-breaker, of the line contactor KY and of the star contactor KY. After a suitable perdetermined period of time, the opening of the contactor KY and of the closing of K allow switching to delta-connection, which is also the configuration of normal running position. These apparatus are affected by currents related to the different starting phases; these currents result to be lower than the rated current of the motor, as illustrated below.