A practical method with high accuracy in generation and application of error values for calibration of current transformer test sets is described. A PC-controlled three-phase power source with a standard wattmeter is used for generating the nominal and error test currents while an electronically compensated current comparator is used to provide summation and subtraction of them, precisely. With this method, any ratio error and phase displacement values could be generated automatically and nominal and test currents could be grounded on the test set safely. Because of its high accurate ratio and phase error generating capability, any type of test set regardless of its operating principles could be calibrated.
The paper presents the special software for transient FE analysis of coupled electromagnetic-thermal problems in a squirrel cage submerged motor working at cryogenic temperature. A time-stepping finite element method and transients analysis of an induction motor has been applied. The non-linearity of the magnetic circuit, the movement of the rotor, skewed slots, and the influence of temperature on electric and thermal properties of the materials has been taken into account. Developed on the basis of presented algorithm a computer program used to analyze the phenomenon of current displacement in the rotor bars of high-voltage cage induction motor working in cryogenic conditions. The results of the simulations are presented.