The phenomenon of cogging torque in permanent magnet synchronous generators with concentrated windings is considered in this work. Dependence of fluctuation amplitude of the torque on width of stator slot opening is researched. The method to reduce the cogging torque by skewing of stator slot and opening of stator slot width equal distance between magnet and tooth on the rotor is described. The construction of this generator is obtained on the basis of numerical simulation results Index Terms-Torque, finite element method, permanent magnet machines.

A clear trend has emerged in the field of wind power industry concerning the creation of low-, medium-, and even high-power direct-drive wind turbines without the use of gearboxes. Such generators are usually multipolar and mostly excited from permanent magnets. In the low-speed performance, multipolarity means a higher specific torque and reliability as well as lower operating costs, which in the case of high-speed generators is hindered by gearboxes. Multipolarity with a high specific torque can be achieved mainly through the use of permanent magnets of high-energy materials (such as NdFeB) and through design solutions for the armature winding. The authors compare two most common types of wind generator's armature windings: the distributed one, which contains a coil embracing several teeth, and the concentrated armature winding -with one coil for one stator tooth. The comparison (along with the experience in developing the wind turbines) shows that the concentrated winding version has a number of advantages, the main of them being the multipolarity. This means that the generator with a concentrated winding can be more acceptable for the direct-drive wind turbines, is easier to make and simpler to operate. Another very important advantage of concentrated windings shown in this work is that they allow achievement of a higher specific electromagnetic torque, which means smaller size and weight of such a generator in the low-speed version.

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The paper presents an overview of brushless electric motors used in hand electric tools and household appliances. Analysis of the motor types has shown that synchronous reluctance motors are the most reliable for lowpower drives of such tools and appliances due to their simple design, long service life and low cost of production. Solutions are proposed for significant decrease in the quadrature-axis magnetic flux of the synchronous reluctance motor. The motors are shown to develop the specific electromagnetic torque up to 0.35÷0.4 Nm/kg.

In the paper, the possibilities to apply synchronous brushless motors in the electric hand tools are considered. The potential of such motors is estimated in a wide range of characteristics. In particular, estimation is made for the electric hand plane with a synchronous motor having outer rotor and excitation from permanent magnets.

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The work considers the issues connected with application of non-overlapping coils in the homopolar inductor machines. The calculation and analysis are performed for the magnetic field in the tooth zone of such a machine, and, based on the results, recommendations are given on the choice of optimal parameters of the tooth zone. The sample under study is a 32 kW experimental inductor generator.