Justification of the appropriate magnetic pre-biasing level in determining the electromagnetic parameters of turbogenerators using the method of dc damping
Background. Currently, the definition of electromagnetic parameters of turbogenerators considering the massive multichannel rotor regulated by paragraph 25.1.4 industry standard 10169-77 “Electrical three-phase synchronous machines. Test methods”. The methodology of experiments and results processing provides for the procedure of preliminary biasing of the magnetic core. Herewith, the value of the biasing current exceeding the initial damping current by 10-50 times is not sufficiently experimentally verified. Materials and/or methods. To develop recommendations on the value of the preliminary biasing carried out in experiments of DC damping in the stator winding of a stationary synchronous machine, a series of experiments on an industrial turbogenerator with a capacity of 100 MW carried out. The study of the effect of the value of the residual magnetic induction in a wide range carried out by preliminary biasing of the path of the main magnetic flux of the machine from the excitation winding. The transition functions checked by modern digital recorders. Results. The research allowed establishing that for the determination of unsaturated values of turbogenerator electromagnetic parameters the experiments of direct current damping should be carried out at preliminary biasing with the current 2,7 times exceeding GOST regulated value. Recommendations for changing the text of paragraph 25.1.4 GOST 10169- 77 “Electrical three-phase synchronous machines. Test methods” describing the procedure of preliminary biasing formulated. Conclusion. To eliminate the influence of individual hysteresis cycles in order to determine the unsaturated values of electromagnetic parameters of synchronous machines with a massive rotor, DC damping experiments should be carried out in the implementation of the procedure of pre-biasing by current which creates magnetic flux in the machine at least half of the flux in idle mode at rated voltage of the stator winding output.