Direct-Drive Contactless Wind Generator with Concentrated Winding

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 con-centrated 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.