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The outcomes of a theoretical transient analysis of a stationary IM during connection to the net work are reported. Based on the obtained analytical expressions, the influence of each component of transient currents and electromagnetic torque on ripple amplitudes and transient time is revealed. The original reason for the long term and high ripple starting torque transient is clarified and possible ways of eliminating them are theoretically justified.

For the in depth analysis of transients in a rotating induction motor the method of constant velocity is proposed, which allowed us to obtain analytical expressions for the currents and electromagnetic torque of the motor when selecting the d-q model as a starting point. The results of the theoretical analysis of transient cur rents and electromagnetic torque at the startup of the induction motor with a cage rotor are shown and the influ ence of the motor rotational frequency on them is determined. The results of the computer simulation of the induction motor startup confirm the validity of the analysis using the method of constant velocity.

The paper deals with problems of selection of structures and optimum design of multipole permanent magnet synchronous machines (PMSMs) for operation in offshore wind-and wave-power plants under severe conditions for maintenance service. It is shown that multipole PMSMs are a new and very suitable electrical machine for direct connected turbogenerators in power plants and, at the same time, multipole PMSMs meet a number of other important demands, including high reliability, contactless construction, high efficiency, minimum mass and dimensions, and cost effectiveness. With the aim of systematization, an integrated classification scheme of PMSMs is presented to describe the variety of designs of stator and rotor configurations. With the help of a theoretical analysis based on a geometrical approach, analytical expressions for PMSM comparison are derived using the relationship between the criterion of optimization (maximum power density) and the main geometric parameters of PMSMs. Comparative analysis of the PMSMs with radial and axial magnetic fluxes for the case of various numbers of poles and different diameters of rotors has confirmed that axial multipole PMSMs are synchronous machines with maximum power density and an optimum variant for direct connected turbogenerator structures for offshore wind-and wave-power plants. It is noted that the advantage of axial PMSMs over radial PMSMs is monotonic growth in accordance with increasing number of poles p. Under the condition that p ≥ 20, which is strictly necessary for designing direct connected turbogenerators in offshore wind-and wave-power plants, we have more than doubled the power density at axial PMSMs as compared with radial ones.