The windmill is a standard green energy conversion system that uses the mechanical input produced by blades that capture the surrounding wind currents, redirecting them in order to create a rotational force that then turns a shaft connected to a generator that produces electrical current. Most often, windmills generate their electricity using a permanent magnet machine, i.e. generator. Standard permanent magnet machines used in industry involve different variations of a rotor stator combination that allow for the production of either a mechanical output (if the input to the system is electrically driven) or an electrical output (if the input to the system is mechanically driven). Research done in the industry of electrical energy production has allowed for overall improvements in system performance, allowing manufacturers to limit issues in in the Multiphysics system such as:
• Magnetics (leakage flux, eddy currents, etc.)
• Electrical Engineering (insulation, windings, etc.)
• Mechanical Engineering (thermal, vibration, etc.)
Despite the complex multidisciplinary nature of a permanent magnet machine and its various different architectures, the commonality between most if not all systems are that there is an air gap between the rotor and the stator( as displayed in the illustration) of the system. Because of air’s low permeability to electromagnetic flux the total amount of current that could be possibly be produced is reduced, resultantly inhibiting the systems overall productive capabilities. This drawback has been combated in industry by manufacturers who have attempted to reduce the size of the air gap between the rotor and stator. However, the tight tolerances that would be needed to prevent the resulting negative effect of the air gap on the systems leads to manufacturing risks, as well as mechanical performance issues when the thermal and dynamic effects are taken in account reducing the system’s reliability, while also increasing the associated costs that come with manufacturing permanent magnet machines.