In various industrial electrical installations, especially those that are overloaded in some way, they can use the star-delta switches, in order to reduce the starting effects of the electrical components. It is valid to emphasize that it is only possible to start an electric motor through star-delta switches, if it has six accessible terminals and has a nominal 597 b double voltage, such as 220 / 380V or 380 / 660V. The process for motor startup is basically done by connecting it in the star configuration until it reaches a speed close to the speed regime, when this connection is undone and the connection in a delta is executed.
In this way, it can be said that the exchange of the connection during the entire starting process is duly accompanied by an increase in current, so that the advantages of its reduction disappear considerably if the switching is anticipated in comparison to the ideal point. During start-up, the torque and starting current may be reduced to 1/3 of their nominal values. In this way, an engine can only start by means of a star-delta switch when its torque on the star connection is greater than the torque of the axle load.