Start-up of the deep-bar motor with the use of the soft start-up an energetistic face

During the soft start-up of the induction motor, various negative phenomena connected with considerable heat emissions in the motor’s winding are observed. They may, particularly in the case of the prolonged start-up, result in a damage to the squirrel – cage winding. What is more, torque impulses may be harmful to the elements of the driving system. The article discusses the use of the soft start-up and indicates that it helps to minimize only some of the negative phenomena. There are cases in which the soft start – up proves to be an additional risk to the motor. The distribution of the energy emitted in particular elements of the motor’s winding has been calculated, both during the start-up with the use of the soft start-up and during the direct on-line start-up, in the deep-bar 320 kW motor. There are giving laboratory tests: time-current, speed, torque and temperature rise of the rotor’s bar in the low-power induction motor during start-up