Investigation of hybrid permanent magnet rotor topology

With increasing concerns about environment, technology is evolving towards more efficient usage of materials. The key is to get better performance with less or the same amount of material. Electric motors are one of the most popular research topics in these concerns because it provides mechanical rotation with electrical excitation which is used in almost every single application in world. Moreover, electrical energy is mostly produced and consumed by electric machines and this makes efficient use of materials building up electric machines very critical. For some decades, with the usage of high performance permanent magnets and electrical steel, permanent magnet electric motors find place in applications where induction machines, electrically excited synchronous mahines and DC (brushed) machines mainly used. Especially with the increased usage of wind turbines and electric vehicles, popularity of permanent magnet machines (both DC and AC) has peaked and this lead to major broadening in the PM motor research field. Many different stator and rotor types are investigated, improved and proposed for obtaining better characteristics by detailed work and pushing the limits. In this thesis, a recently propesed hybrid permanent magnet strcture is investigated in order to determine the limits and capabilities. In the literature view part, history of electric machines are broadly mentioned and then detailed literature scan is made for hybrid motors where various motor topologies are represented. Later, theory of permanent magnet machines are studied which were then used in the design part. For the design part, two different stator structures are investigated: fractional slot and integer slot. A surface permanent magnet motor which is used as benchmark motor with fractional slot is analyzed following by the design of an internal permanent magnet (V-type) motor with the same size. After that aforementioned hybrid motor is designed and optimized. For the integer slot part, by using the analytical equations, a surface permanent magnet motor is designed. By using the geometric quantities of the motor an internal permanent magnet motor is designed and optimized by varying magnet shape and position. After the design of IPM motor is completed, by implementing SPM and IPM magnets into the same rotor initial hybrid motor is formed. By appyling wide range optimisation, final hybrid motor design is obtained. After the design phase is completed, integer slot motor is resized for prototyping. A prototype is built and tested in laboratory. Fine agreement between analysis and test results is obtained. Investigated hybrid rotor topology for fractional and integer slot stators are compared with their consequent benchmark surface and internal permanent magnet motors. It is obtained that by using hybrid rotor structure with integer slot stator, it is possible to obtain better performance characteristics in terms of total harmonic distortion and torque ripple.