Combined Methods to Overcome Unbalanced Magnetic Pull in Fractional Slot Electric Machines

Fractional slot is proven to be more effective than integral to minimize cogging torque problem in electric machines, especially wind turbine application. However, the issue of unbalanced magnetic pull associated with fractional slot is a big challenge for academia and industry which cannot be solved until now. This paper aims to propose a solution to overcome and reduce unbalanced magnetic pull problem using a combination of techniques, which can also minimize cogging torque, vibration, noise and flux leading to optimum performance and efficiency. The combined methods are using axial channels, stator opening width, shoe height, hollow titanium shaft, and stronger side core cover. Finite element, autocad, and design of experiment are used to present the design, analysis, optimization and results, then validated by Maxwell formula.