NON=LINEAR OSCILLATION OF SYNCHRONOUS MACHINE

Abstract

Application of the small oscillation theory for studying self and forced oscillations in a synchronous machine is well known. If the oscillation is large this linear theory loses. its validity since the current, voltage and torque no longer vary proportionately. The machine oscillation is then classified as non-linear. Here is an attempt to analyse a large nonlinear oscillation and to determine the torque variation resulting from a known load angle variation of large amplitude. Park's equations of the d-q axes voltages are rigorously solved for the axes flux linkages, the axes voltages are expanded into infinite series using Bessel's functions and the flux linage co-efficients are written down. Using operational impedances current coefficients are calculated and finally torque is evaluated. Constants of a laboratory synchronous m^chine are deter-:fined accurately. Using the analysis developed its torque is computed for a large load-angle oscillation of lo,,, frequency. Attempt is also made to develop an experi:jental technique to verify the validity of the lr4rge oscillation theory. As a r quirenent, a load anle recording device3 a low-frequency oscillation-generating device and a trque recording device are designed using siur)le principles, and constructs,'. Using these apparatus an experimental set-up is arranged to record the torryue and current variation for a known load angle variation. ileasurinr from the oscillograrns the departure or otherwise of the torque and/or current from the theoretically estimated value is graphically repro s9nted.