COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering

Purpose – This article seeks to present the simple and easy to manufacture design of a permanent magnet generator based on coreless windings. An example is shown of basic calculations based on an equivalent magnetic circuit. Finally, a description of a 20?kW prototype of PMSG is presented based on rectangular magnets which contains mechanical design and experimental results.

Design/methodology/approach – The analysis presents flux dependence using several parameters such as: magnet's grade and size in comparison with coil and air-gap dimensions. The second part of the article concentrates on simulation results of Finite Element Method analysis (FEM) that clearly shows the flux distribution for different magnet shapes – trapezoidal and rectangular.

Findings – The presented topology of the machine has several advantages, e.g. there is no starting and cogging torque which is very important especially for wind power systems because of the start up point of the turbine. Moreover, it is cheap and easy to manufacture because of ironless technology in stator. The generator can be produced in the range of single watts up to hundreds of kilo watts of power in multi disk operation.

Research limitations/implications – The ironless technology applied to the stator, results in the need for using stronger magnets in comparison with a classic iron-core permanent magnet machine.

Practical implications – This axial-flux machine seems to be very interesting for low speed power generation systems such as wind and water turbines. Cost effective permanent magnet generator can be used for local power generation (e.g. heating). The generator can also be connected to the main grid through a special grid-tie-inverter.

Originality/value – The article presents the simple and rarely presented topology and describes a few methods of optimisation of the parameters to achieve maximum power.