Tkachenko S. The thermal protection of induction motor's cage rotor, based on the current regime parameters control

Object - thermal processes in induction motors with skin-effect current in the short-circuited rotor winding. Goal - the development of microprocessor thermal protection of squirrel cage induction motors power through the control parameters of the current regime. Research methods and apparatus - the theory of electrical circuits, numerical methods for solving systems of nonlinear differential and algebraic equations, digital signal processing techniques and methods of the transient ac machines, ADC, PC. Theoretical and practical results - agreed to actual scientific and technical job creation thermal protection cage rotor on the basis of the control parameters of the current regime of high-power induction motors with a significant manifestation of the skin-effect current in the rotor, which can increase the reliability of the system auxiliary power plants. Novelty: We introduce the new method of rotor temperature indirect measurement for the induction motors with the skin-effect in a squirrel cage rotor, on the base of the temperature-dependent component of its resistance, which is determined according to the measured instantaneous values of phase currents and voltages, rotor slip and by well-known dependence of rotor resistance from slip value for the cold state temperature. We have improved the equivalent circuit for the rotor thermal protection, which is differences by allocation of individual active-inductive circuit to evaluate losses in the steel, and by formulating the rotor resistance as functions, which depends not only on the slip, but also on the temperature. We have established that in the dynamic motor operation state, an extra measurement of the stator currents derivatives can improve the accuracy of indirect determination of the rotor temperature by allowing additional losses in the differential-integral equations of the stator and rotor contours. To eliminate the errors of the voltage unbalance, the indirect measurement method of the rotor heating temperature has been further developed by determining the input resistance from the positive sequence currents and voltages. The degree of implementation - methods of experimental determination of the heating temperature of cage rotor induction motor based on the control parameters of the current regime in place at Zuevsky TPP Vostokenergo and the Institute UkrNIIVE. Industry of use: energy, electric power stations.