Electrical Engineering ⇒ Topic : V-curves of a Synchronous Motor

V-curves of a Synchronous Motor

                              Figures shows Families of V-curves for a synchronous motor

• It has been stated above that, when the field current is produced which exceeds the minimum current at unity power or at normal excitation.Similarly, when motor is over-excited, the armature current also rises and exceeds the current required at normal excitation to develop the necessary torque,at any given load.
• By applying a given constant load to the shaft of a synchronous motor and varying the field current from under-excitation to over-excitation, recording the armature current at each step, the curves of Fig.(a) are obtained. The A.C. armature current is plotted against the D.C. field current for no-load, half-load, and full-load values, respectivley. Fig. 15.13 (b) shows the relation between power factor and field current for various loads.
• The V-curves (shown in Figure) represent the phasor diagrams and vice-versa for various conditions of load and power factor