polepermanent magnet synchronousmachines

The development ofNeodium-Iron-Boron and Samarium-Cobalt magnets hasmadeitpossible tousepermanent magnetseveninlargesizemotorandgenerator applications. Oftena permanent magnetsynchronous generator (PMSG)is vectorcontrolled andindirectly connected tothenetworkvia powerelectronic converters. Industry, however, hasa great interest onapplying PMSGswithout powerelectronics invarious powergenerating applications suchasgenerators insmallwater powerplants, ships andsubmarines. PMSGs havepermanent excitation thatcannotbe regulated. Therefore a properly designed damperwinding isrequired toachieve stable operation without afrequency controller. Thispaperpresents analysis andperformance characteristics ofnon-salient polethreephasepermanent magnetacmachines equipped withdamperwindings inrigid networkoperation. By analyzing theresults given byatwoaxis vector equivalent circuit basedsimulation modelofthePM-machine, theguidelines for efficient damperwindingparameters fornetwork-connected generators arefound. Itisobserved thatthere exists anoptimum valueforthedamperwinding resistance whichresults instable operation after transients intheshortest period oftime.The optimum valueofthedamperwinding resistance isdependent on theelectrical andmechanical parameters ofthedrive. Theeffects ofthePM-machine electric parameters andtherotorinertia for optimumdamperwindingresistances are analyzed. The theoretical results arevalidated bypractical experiments carried outona5.2-kWprototype permanent magnetmachine equipped withdamperwinding.