| Abstract |
The electrical drives constituted by an induction motor fed throuqh a voltaqe source inverter may present problems related to current harmonics introduced on the D.C. link; that may pose environmental problems, particulary in traction applications, in qeneral filterinq problems which sometimes may be particularly onerous, or problems due to torque pulsations. Those aspects may result even more important for the case of motor supply technique of the type six-steps or similar, which may constitute a good solution for a wide field of applications. A technique which allows of increasing the harmonics frequency and affecting the noise problems, without alterating the inverter's commutation frequency, is the one based on the choice of a motor phases number greater than three. In such conditions the phases number may be considered a new free parameter which has to be optimized; a general discussion on such argument has been performed by the authors mainly with regards to the basic problems related to the different phase connection techniques, which are possible when the phases number increases. The new different solutions, for a wide range of the phases number M and the choice of their connecting methodologies, are analysed in the paper under the point of view of the effects on the D.C. link harmonic contents, and on the torque pulsations amount. |
