• Energy Research

Currently there is no information about the level of cycle time and the duty rating effects on a thermal state and insulation live of induction motor drive, which essentially influences on service reliability. The electrothermal model, which allows considering peculiarities of electromagnetic energy transformation in thermal energy, heat transfer and heat exchange processes, was used for calculation and analysis of the thermal state of induction motor drive. The research has approved that the magnification of cycle time and high value of working slips of the induction motor drive leads to essential growth of its temperature. The estimation of the insulation live which has displayed lowering of the insulation live indexes to 12 times — for the rated induction motor slip s=0.1 and to 50 times — for working induction motor slip s=0.9. Correction current coefficients of the induction motor are defined, supporting its rated thermal conditions.

Theoretical researches and simulation results, which based on numerical realization of the finite element method of three-dimensional transient mathematical model of the electrical and magnetic fields in induction motor which displayed the features of the processes of AC energy conversion in the experimental short-circuit mode are obtained. Through the implementation of the dynamic spatial model of electromagnetic fields by the finite element method and numerical simulation data of the short-circuit dynamic mode of the induction motor, the parameters taking into account the structural features of the stator and rotor, and the nonlinear properties of active materials in the multicomponent modeling domain of its substitution circuit are determined. It is proved, that the new approach to the determination of the substitution circuit parameters of induction motor based on simulation data field provides a significant increase in accuracy compared to conventional iterative-empirical methods.

The power systems must satisfy the requirements both for high reliability and efficiency. The main component of the shop power supply systems is a busbar. There have been certain engineering techniques for the estimation of parameters, voltage and power losses, characterized by having a high error. Other methods have had a significant calculation efficiency, but without allowing the voltage drop to be determined as a function of the network power factor. Therefore, the aim of this work was to develop an approach that allowed an accurate estimation of the parameters and voltage drop in trolleys, depending on the network power factor. This approach was based on the decomposition of the electromagnetic processes in a trolley busbar by connecting one phase to estimate both the resistance and reactance in the absence of the external field, and two phases to estimate the resistance and reactance in the presence of the external field. The most significant results were the determination of the resistances and reactance, depending on the frequency of the current harmonics and the distance between the phases of the busbar. The dependences were proposed to estimate the resistance and reactance for the corresponding phases and current harmonic. The analytical expression of the ratio between the voltage drop in trolleys and the power factor of the network was obtained. The testing data confirmed the high accuracy of the proposed approach. The significance of the results composed a more precise determination of the parameters and voltage drops in each phase of trolleys, irregardless of their location, number, shape, as well as the phase currents’ non-symmetry, wasting no time for the field simulation

The presence of higher current harmonics has a negative impact on the efficiency and reliability of the elements of network. Higher current harmonics can lead to significant increases of resistance, voltage drop and active losses in busbar, also to decreasing network power factor. Existing engineering techniques can’t provide a reliable calculation of the parameters of busbars at higher current harmonics influences. Therefore, the aim of the work is to develop a new approach of parameters determination and the voltage drop estimation in busbar at higher current harmonics influence. Mathematical model of electromagnetic processes in busbar, which takes into account their design features, non-linearity of magnetic and electrophysical properties, proximity effects, surface and external surface effects, was developed and proposed. This model will allow to determinate the components of active and reactive resistances of busbar, voltage drops for each eigenvalue of the amplitude and frequency of current harmonics. Based on field simulation results was obtained the functional dependence in bicubic polynomial form. For effective spectra and amplitudes of higher harmonics, at selecting the corresponding polynomial coefficients, it will allow to determinate the components and the resulting values of voltage drops for an individual busbar’s design without spending time on field simulation. Based on the proposed approach, a method will be developed for the busbar's parameters identification and voltage drop estimation. This will allow effectively define the network configuration, installed capacity of compensating devices, which will provide the reliability of electrical collectors with the declared technical data and etc.