Direct-Drive Contactless Wind Generator with Concentrated Winding

Abstract

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.

Skewing angle magnet and coil reduced starting torque in a permanent magnet synchronous generator for a small vertical axis wind turbine

“…The increased attention to the winding possessing sufficient length, with overlapping frontal connections, has led to an increase in growth, with an increase in copper consumption and eddy current losses. This is a disadvantage, has it has led to a synchronous generator with non-overlapping concentration windings for wind power (Saavedra et al, 2014;Levin et al, 2012;Magnussen and Sadarangani, 2003). Based on the PMSG generator producing high starting torque values, and a dependency of the torque to be related to the rotor's rotation angle (Bakiev et al, 2018).…”

Methods to reduce cogging torque of permanent magnet synchronous generator used in wind power plants

“…Another well-known cogging torque reduction method is the skewing of the stator teeth or the rotor magnets [10], [12], [22], [23], [32], and [33].…”

“…Latest trend is to use the PMSG with non-overlapping [10], [21], [25]- [30]. The production technology of non-overlapping concentrated windings' insertion in stator (armature) teeth with opened or halfopened slots is comparatively simple.…”

Efficiency estimation for permanent magnets of synchronous wind generators

“…At the same time, it could be pointed out that under consideration here will be only the synchronous generator whose armature winding is made concentrated, in the form of toothed coil as providing a higher specific power of the electric machine [8,9].…”

“…Therefore, the optimal form of the tooth zone can be achieved via the open slots; besides, this allows applying in particular cases cheaper and more reliable low-energy magnets (e.g. of ferrite-barium or ferritestrontium [8,9,11]). …”