ahalf-w***ephase-controlledthyristortypeAutomaticVoltageRegulator(***R)andformspartoftheexcitationsystemforabrush-lessgenerator.Inadditiontoregulatingthegeneratorvoltage,the***Rcircuitryincludesunder-speedandsensinglossprotectionfeatures.Excitationpowerisderiveddirectlyfromthegeneratorterminals.Positivevoltagebuildupfromresiduallevelsisensuredbytheuseofefficientsemiconductorsinthepowercircuitryofthe***R.The***Rislinkedwiththemainstatorwindingsandtheexciterfieldwindingstoprovideclosedloopcontroloftheoutputvoltagewithloadregulationof+/-1.0%.Inadditiontobeingpoweredfromthemainstator,the***Ralsoderivesasamplevoltagefromtheoutputwindingsforvoltagecontrolpurposes.Inresp***etothissamplevoltage,the***Rcontrolsthepowerfedtotheexciterfield,andhencethemainfield,tomaintainthemachineoutputvoltagewithinthespecifiedlimits,compensatingforload,speed,temperatureandpowerfactorofthegenerator.)