Pole-Changing Windings for Close Ratio and 1:N Ratio Using the 3//Y / 3//Y Method

Requirement for pole-changing motors emerged at the very early times of asynchronous motor design. Different solutions have been elaborated and some of them are generally used. One of these solutions in use is the so called pole phase modulation method. The so called 3 Y / 3 Y pole-changing winding being subject of this paper belongs to this group. This paper presents a new approach to this method. A new, complete and comprehensive study is introduced, including features and, moreover, detailed design guidelines. The method is applicable for any pole combination for the so called close ratio without any further particular consideration. As the target of the paper is to provide solution for high power application, it does not deal with balancing methods, but as a novelty, calculates the effect of those disadvantageous phenomena (asymmetries, even harmonics) in order to enable the designer for evaluation and decision. The study also reveals as a novelty that the same method is suitable for wide ratio as well, moreover, a new solution for theoretically infinite ratio expressed in 1:N, with supply voltage system of N phase is proposed. Using this motor, a new and complete drive system has been proposed with subject pole changing motor as core element as the most appropriate arrangement of high power main marine propulsion drive.

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