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The past thirty years have been an exciting period with tremendous advances in the development of interior permanent magnet (IPM) electrical machines. Over the course of this period, interior permanent magnet synchronous machines (IPMSM) have expanded their presence in the commercial marketplace from few specialized niche markets such as machine tools, air conditioner compressors, servo drives to mass-produced applications, including high-efficiency electric traction drives for the latest generation of hybrid-electric vehicles (HEV). Power ratings of available IPM motor drives have dramatically expanded by approximately three orders of magnitude during this period, now reaching power levels up to 1 MW ratings. Closer examination reveals that several different knowledge-based technological advancements and market forces have combined, sometimes in fortuitous ways, to accelerate the development of the impressive IPMSM drives technology that we find available today. The purpose of this paper is to provide a broad explanation of the various factors that lead to the current state-of-the-art IPM technology, and to illustrate its application success in the commercial sector, including automotive industry.