Energy aspects and monitoring of asynchronous motors starting

Very important are the energy analyses at the rheostatic starting of the existing wound rotor three-phase asynchronous motors, used for driving the long belt-type carriers, which have a difficult and long-duration starting. A factory producing static converters proposes to the customer a modernization of the starting by using a single-phase rheostat and a three-phase bridge in the rotor. That is why, the authors of the paper have carried out this study which analyzes the classical rheostatic starting and the starting proposed as a modernization. The investment aspect and the costs of the whole starting period have been analyzed on the basis of the data filled in the technical card of the machine. The paper contains some simulations with quantitative and qualitative information regarding the electrical energy losses and the duration of the starting, which are an important percent in the operation expenses. The modernization proposed by that factory for the asynchronous motor analyzed here means that the expenses afferent to the starting process exceed with 10.7% the existing variant. The measurements performed in the laboratory for the rheostatic starting of a low power asynchronous motor, attest the validity of the mathematical model and of the simulations presented in the paper.