Synch. Machine on infinite bus: Lag Generator Generator U.P.F. line Motor line of power stability limit Lead Generator V EV/ZS V2/ZS Lead Motor Loci of constant active powers Lag Motor Loci of constant EMF
Synch. alternator capability curve Armature heat limit locus Q Field heat limit locus U.P.F. line P V Q V2/xS Emax V/xs P Synch. alternator capability curve
& neglecting saturation: Neglecting ra w.r.t. xs Approximately, at constant active power: - The EMF phasors represent field currents - The axs phasors represent armature currents at different power-factors
& neglecting saturation Neglecting ra w.r.t. xs Approximately, at constant active power: - The EMF phasors represent field currents - The axs phasors represent armature currents at different power-factors
& neglecting saturation Neglecting ra w.r.t. xs Approximately, at constant active power: - The EMF phasors represent field currents - The axs phasors represent armature currents at different power-factors
& neglecting saturation: Neglecting ra w.r.t. xs Approximately, at constant active power: - The EMF phasors represent field currents - The axs phasors represent armature currents at different power-factors
& neglecting saturation: Neglecting ra w.r.t. xs Approximately, at constant active power: - The EMF phasors represent field currents - The axs phasors represent armature currents at different power-factors
& neglecting saturation: Neglecting ra w.r.t. xs Approximately, at constant active power: - The EMF phasors represent field currents - The axs phasors represent armature currents at different power-factors
& neglecting saturation: Neglecting ra w.r.t. xs Approximately, at constant active power: - The EMF phasors represent field currents - The axs phasors represent armature currents at different power-factors
& neglecting saturation: Neglecting ra w.r.t. xs Approximately, at constant active power: - The EMF phasors represent field currents - The axs phasors represent armature currents at different power-factors
& neglecting saturation: Neglecting ra w.r.t. xs Approximately, at constant active power: - The EMF phasors represent field currents - The axs phasors represent armature currents at different power-factors
& neglecting saturation: Neglecting ra w.r.t. xs Approximately, at constant active power: - The EMF phasors represent field currents - The axs phasors represent armature currents at different power-factors
& neglecting saturation: Neglecting ra w.r.t. xs P=1 pu P=0.75 pu P=0.5 pu & neglecting saturation: Neglecting ra w.r.t. xs Approximately, at constant active power: - The EMF phasors represent field currents - The axs phasors represent armature currents at different power-factors & & Note: Motor & generator curves are actually different due to the effect of losses an other neglected parameters 13
Further Problems (to be tackled graphically & analytically during tutorials of 28 & 29 December 2015): 1) 3 phase Y alternator has armature resistance and reactance per phase of 0.4 & 6 . The machine is connected to an infinite bus at 10 kV and delivers 3 MVA at 0.8 lag p.f., If the machine is operated at constant active power, and changes in losses are neglected, find the % change in excitation needed to attain unity power factor operation. 2) 3 phase Y Synch Motor has armature resistance and reactance per phase of 1 & 30 . The machine is connected to an infinite bus at 11kV and takes 60 A, Find: Active power intake, EMF for 0.8 lag p.f.,EMF for 0.8 lead p.f.