A start is made with the engine warm, with the windings at regime temperature, simulating the case in which the first engine start is failed, for example, by the shutdown of the protection, thus allowing a second attempt to follow. The second condition occurs in the event of an accidental shutdown of the motor in normal operation, for example due to a lack of power in the network, allowing it to continue operation soon after the energy is restored. Therefore, due to the considerably high starting current of the induction motors, the time required in the acceleration of high inertia loads can result in the rapid raising of the temperature of the electric motor.
If the interval between successive starts is reduced, this factor can cause a considerable increase of excessive temperature in the winding, being able to damage or reduce its durability. The official standards lay down a minimum starting system (S1), which engines, regardless of their category, must be able to meet. Two successive departures, the first one being performed with the engine cold, that is, with its windings at room temperature, and the second following after the engine has decelerated until the moment of rest.