ABSTRACT
In PM machines, the dc Ÿeld is replaced by modern hard PMs having good magnetic ¹ux density and very large coercive force. že PM machines consist of both PM generators and PM motors. že PM dc generators are hardly used in recent times. že need is met by the large-scale availability of power electronics-based ac-dc rectiŸer converters. že applications of PM ac generators are also somewhat limited, as most of the large electric utility generators do not use PM excitation systems for various reasons. PMs are employed in diesel/gas-based PM ac generators for isolated standard ac power supply sources at construction sites, etc. In recent years, the PM ac generators are used in automobiles as starter/alternator in standard cars and recently in hybrid electric vehicles for charging the on-board battery modules. že PM ac generators are of speciŸc application types. Recently, higher rating wind generators with surfacemounted PMs (SPM) are getting introduced in wind energy systems. žus, with the scope of PM ac generators being limited, these will not be covered in this PM machines chapter.
