Vol 90, No 1 (2019)

This article examines the characteristics and structure an asynchronous motor with a double-layer rotor for ship electric pumping units, as well as approaches to studying it. The main technical requirement for such motors is a low level of noise emission when providing the required heat removal from the operating motor. The use of an external double-layer rotor in this motor makes it possible to significantly improve its working and maintenance characteristics.

The failure of high-power synchronous motors leads to significant financial losses. This is of great importance for synchronous generators operating in high-power electrical networks and having an effect on a great many consumers. Sudden failure of the high-power generator results in heavy fines and repair costs, malfunction of the power-supply systems, and electric users. Troubleshooting of the equipment is aggravated by many interrelated factors. The method of measuring the external electromagnetic fields, which is widely used for the induction motors, is not used in practice for synchronous machines. Installation of field sensors inside the synchronous machine is not always possible, and measurement of external fields has weak methodological and factual bases. Simulation of the synchronous machine allows tracing the connection of a particular defect with the distortion of the external electromagnetic field of the machine. Full-scale experiments show the actual feasibility of measuring the magnetic fields in the off-synchronous generator housing. Investigation of an external electromagnetic field’s connections with specific machine defects, development of field measuring procedures and processing of the measurement result, and uncovering the diagnostic properties characterizing the state of an operating synchronous machine and allowing making a required decision, is an important scientific and technical issue.

Most energy-efficient control algorithms impair the dynamics of the control system (CS). The most popular of these algorithms is the maximum torque per ampere (MPTA). The low power consumption of the electric drive is achieved by reducing the rotor flux linkage level. Improved algorithms help improve the dynamic performance of control systems without making them less efficient. The three considered possible approaches to ensuring the advanced dynamics of the control system are to sustain the current along the q axis, sustain the motor shaft torque value, and transform the torque command from a steplike function to a sloping straight. The procedure of estimating allowable stator currents with voltage constraints is presented, as well as its possible implementation in an improved energy-efficient control algorithm. The results allow using the suggested algorithm in the induction motor CS in systems with raised requirements on dynamics.

A method for synthesizing control laws that allow minimization of the required capacity of an autonomous power supply of an electric drive based on electric accumulators and/or ultracapacitors is proposed for electric drives that implement an designated programmed motion. The control laws allow disconnection from and connection to the power supply line of one of the sections of the drive’s power supply. The reduction in the required supply of energy in the power source is achieved by more completely emptying part of its sections in traffic areas with a lower level of the requested voltage and conserving a high potential for the forthcoming traffic areas in only one section or parts of sections. A mathematical formulation of the problem is presented, and a numerical method for solving it is proposed. An example of imlementation of the proposed method is considered. It is shown that the proposed method enables a significant reduction in the required capacity and, as a consequence, in the dimensions, mass, and costs of autonomous power supplies of electric drives.

An engineering approach to the approximate calculation of the thermal energy in the flash plasma channel and on the massive metallic electrodes of an air heavy-current switchboard (HCS) of atmospheric pressure, as well as the electric erosion of HCS electrodes that are part of a high-voltage electrophysical plant (HVEP) with a powerful capacitive storage, was proposed. The specific difference of this approach is that, for determination of the energy release and erosion of electrodes in an air HCS, it is necessary to have the data on the electrical and thermal and physical characteristics of metal of the electrodes, specific conductivity of the low-temperature plasma in the flash channel and peak and time parameters of the pulse current in the discharge circuit of an HVEP with a CS. The concept of equivalent active impedance of the plasma channel of a high-current flash stable within the whole CS discharge period on the electric load was introduced and determined mathematically. The electrophysical transference process of the ionized atoms of the melted metal of the switchboard electrodes on the cathode of the studied HCS was approximately considered. The proposed approach allows making a quick evaluation of the electrical energy balance in the HVEP discharge circuit with a CS taking into account the thermal losses in the switchboard. Experiments prove the reliability of the obtained design ratio for estimation of the energy release and erosion of metal electrodes in an air switchboard.

The existing methods for the calculation of electromagnetic processes in the system of current feeders in a graphitization furnace and of busbar packages in a furnace loop require making substantial assumptions, which significantly distort the real picture and do not meet modern accuracy requirements. The use of three-dimensional field modeling is restricted by the stability of computational processes, as well as by a significant expenditure of computational resources and time. In this paper, a numerical simulation of the conjugate spatial electric and magnetic fields in the area of furnace loop busbar packages, current feeders and the core of ac graphitization furnaces using a finite element method. A novel method has been developed for decomposition and dynamic synthesis of parameters according to the criterion for minimizing the current error to the calculate the electrical circuits of power supply systems for electric resistance furnaces with direct heating. The method provides a high accuracy in the calculation of active and inductive resistance and a decrease in active power and magnetic field energy according to the data of three-dimensional numerical-field simulation of complex systems for the furnace-loop busbar packages, current feeders, and core of a graphitization furnace. Criteria are determined for the decomposition of three-dimensional domains of ac conductor systems having a complicated spatial-and-geometric configuration in the subdomain. The application of the finite element method and the decomposition of the 3D domain of the furnace loop for a low-power ac graphitization furnace has provided a high accuracy and computational efficiency of the numerical implementation of three-dimensional electromagnetic field modeling. The relative errors of the method do not exceed 0.35% for the magnetic field energy, 1.45% for the electrical loss, 1.48% for the voltage drop modulus, and 0.67% for the voltage drop phases compared with the numerical values from field simulation of the furnace loop electric circuit. The proposed method can be used to calculate the parameters of electrical machines and short electrical grids characteristic of arc steel-smelting furnaces.

Violations of regulatory requirements for the quality of electrical energy are regularly exhibited in Russian high-voltage electric grids. This leads to particularly negative consequences in areas with electrified ac railways, which are a powerful source of distortions, including the emergence of current unsymmetry. This paper describes the process and the causes of intermittent current unsymmetry as a conductive disturbance generated by the traction substations. Characteristics are proposed for the evaluation of this unsymmetry. An analytical expression is derived for determining the angle between the symmetrical components of the currents in the busbars of the traction substation. It is shown how the change in the electrical load of the traction grid affects this angle. By the example of a single traction substation model, the correctness of the proposed analytical expression is confirmed, taking into account the used assumptions.

A method is proposed for implementation of the most popular hysteresis model, the Jiles–Atherton model, which has a number of advantages over other models. A technique for optimization of the parameters of the hysteresis model based on a real coded genetic algorithm is presented. The method is implemented in two stages. The first stage involves preliminary estimation of the model parameters and the range of their variation. The second stage is the direct implementation of the genetic algorithm. The criterion of convergence is based on the achievement of a preset value of the standard deviation and the maximum permissible number of generations. The genetic algorithm was implemented with 50 individuals. Each individual is associated with four variables that correspond to the hysteresis model parameters. The maximum number of generations was set to 50 and 100. The initial probabilities of the crossover and mutations were set to 90 and 5%, respectively. A specific feature of the proposed implementation of the genetic algorithm consists in internal optimization of the fifth parameter for each individual of the population. The computer code was developed using the Delphi environment. Comparison of the experimental and simulated curves showed good agreement. A method that involves preliminary estimation of the parameters and further application of the genetic algorithm yields rather accurate results, is easy to implement, and provides a high data-processing speed.