Design of an interior permanent magnet machine with concentrated windings for field weakening applications

This thesis presents the design of an interior permanent magnet (IPM) machine with concentrated windings (CW) for field-weakening applications. The initial phase of this work involved a feasibility study and comparison with the CW surface permanent magnet machine. Subsequently a CW-IPM machine was designed and constructed with the aim of achieving a wide constant power speed range (CPSR). Lastly, based on the constructed design, scalability and efficiency studies were performed.The work done in this thesis has led to the successful construction of a prototype machine achieving a very wide 7.2:1 CPSR. At the time of writing, there is no available literature that clams such a wide CPSR in a concentrated wound permanent magnet machine. Distributed winding machines capable of achieving such a CPSR have complex rotors and hence manufacturing issues. The proposed design was subjected to the same size constraint as two previously constructed 550W distributed winding IPM machines. With this constraint, the advantage of shorter end winding length was exploited and the effective length of the machine was increased. This resulted in a significant increase in output power to 800W throughout the CPSR. A detailed study on losses performed in this work showed that despite the increased harmonic content generated by CW, frequency related losses can be minimized through design methods, and over an 80% efficiency can be achieved throughout the CPSR. Mechanical stress analysis of the rotor indicated that iron bridges were required between poles to prevent excessive stress inflicted on the inter-pole link sections during high speed operation.Based on confidence gained from the experimental verification of the CW-IPM machine design, a scalability study was performed and designs up to 30kW were proposed. A study on efficiency optimization was also carried out and the prototype machine was redesigned to produce up to 93% efficiency.The work done in this thesis has setup a strong basis for future work on CW-IPM machines for automotive traction drives and has also proven that this machine type is suitable for high performance industrial applications requiring high efficiency over a very wide CPSR