The direct drives of electric motors are realized through keys of the type star-triangle, only becoming recommendable to be realized if it has six accessible terminals and still have dual voltage nominal, as 220 and 380 V or 380 and 660 V. In the case of star startup, the torque and starting current shall be reduced by 1/3 of their nominal values. Therefore, an engine can only be able to start by means of a star-delta key when its torque on the star connection is greater than the torque of the axle load.
Thus, the process used to start the motor definite motors mrosupply is initially accomplished by connecting it in the star configuration until it reaches an approximate velocity of the regime velocity, when this connection is undone and the triangle is executed. The switching of the connection in the starting process is accompanied by a current rise, so that the advantages of its reduction are canceled if the switching is anticipated in relation to the ideal point. In industrial electrical installations the star-delta type switches can be used to soften the starting effects of the electric motors.