Model of pulsating current traction motor taking into consideration magnetic losses in steel

The aim of the work is to develop a mathematical model of the traction motor of the pulsating current of an electric locomotive taking into account the magnetic losses in the motor steel to determine the starting parameters depending on the voltage of the armature winding. Methodology. Mathematical modeling of electromagnetic processes in a traction motor of pulsating current is applied taking into account the nonlinear nature of the armature inductance, the inductance of the excitation winding and the nonlinear nature of the universal magnetic characteristic. The magnetic losses in the steel of the traction motor were taken into account by establishing the dependence of these losses on the frequency of reversal, the magnetic flux in the magnetic circuit of the motor and the geometric dimensions of the motor. Results. The mathematical model of calculation of starting parameters of the traction engine of the pulsating current of the traction drive of the electric locomotive of alternating current taking into account the equation of instantaneous value of losses in engine steel is developed. The dynamic characteristics of the traction motor with pulsating current are obtained. It allows to investigate starting parameters of the traction engine on the basis of the received mathematical model and to design elements of the traction drive of the electric locomotive according to the specification, to choose optimum design parameters. Originality. For the first time a comprehensive study of the pulsating current traction motor was carried out taking into account the nonlinear nature of the armature inductance, excitation winding inductance and nonlinear nature of the universal magnetic characteristic and taking into account the magnetic losses in the motor steel. Practical significance. The model of the traction motor of pulsating current taking into account losses in steel of the engine on the basis of the carried-out calculation is developed. Experimental studies have confirmed the adequacy of the model, which allows to apply the obtained model to develop a mathematical model of an AC electric locomotive to study the electrodynamic processes in it at different modes of operation of the electric locomotive.

Fluxgate Sensors for Onboard Weighing Systems of Heavy-Duty Dump Trucks

The article reviews the results of the authors’ research on the possibility of using the magnetic field strength generated by DC traction motors as a useful signal carrying information about weight of cargo transported by a mining dump truck.The objective of the research was to find a way to determine weight of cargo carried by a mining dump truck. In contrast to the existing onboard weighing systems, it becomes possible to create a compact autonomous device that does not require integration of sensors into the body structure and electrical circuits of the truck.Problems of increasing the efficiency of measuring devices based on fluxgate converters are considered with the view of using them as onboard systems for estimating cargo weight. The sensitivity of the fluxgate sensor can be increased by increasing both the amplitude and the effective value of the voltage applied to its excitation winding. The proposed original circuit for feeding the fluxgate sensor’s excitation winding from a modulated signal generator made on logical elements allows increasing the voltage supplied to the fluxgate sensor’s excitation winding without increasing the supply voltage, and by increasing voltage surges at the fronts of rectangular modulated high-frequency pulses, as well as due to resonant phenomena. The use of such a generator excludes the influence of the fluxgate sensor’s excitation winding on the generator frequency, since the frequency of modulating signals becomes the operating frequency of the fluxgate sensor, and it remains unchanged. The increased sensitivity makes it possible to install the sensor in any convenient place in the dump truck cab, and not in the immediate vicinity of traction motors.Evaluation of cargo weight is carried out during movement of the dump truck along the control section of the road. The readings are taken from an ammeter (milliammeter), the scale of which is pre-calibrated in mass units. Measurements of mass should be carried out under the same modes of dump truck movement and with the same location of the fluxgate sensor as when calibrating the scale of the measuring device. The control section of the route on which the measurements are carried out must be the same or similar to the one on which the measuring device was calibrated.The proposed device is distinguished by ease of use, is characterised by low energy consumption, is compact, does not contain expensive elements and does not require careful maintenance.

Inverter Volt-Ampere Capacity Reduction by Optimization of the Traction Synchronous Homopolar Motor

The synchronous homopolar motor (SHM) with an excitation winding on the stator and a toothed rotor is a good alternative to traction induction motors for hybrid mining trucks. The main problem in the design of the SHM electric drives is that the magnetic flux forms three-dimensional loops and, as a result, the lack of high-quality optimization methods, which leads to the need to overrate the installed power of the inverter. This article discusses the procedure and results of optimization of a commercially available 370 kW traction SHM using the Nelder–Mead method. The objective function is composed to mainly improve the following characteristics of the traction SHM: total motor power loss and maximum armature winding current. In addition, terms are introduced into the objective function to make it possible to limit the voltage, the loss in the excitation winding, and the maximum magnetic flux density in the non-laminated sections of the magnetic core. As a result of the optimization, the motor losses and the maximum current required by the motor from the inverter were significantly reduced. The achieved reduction in the maximum current allows the cost of the IGBT modules of the inverter to be reduced by 1.4 times (by $ 2295), and also allows the AC component of the DC-link current to be reduced by the same amount.

ESTIMATION OF THE MASS OF CARGO DUMP TRUCK

The article discusses an on-board weighing system for the load of a mining dump truck, which simplifies measurements and, unlike existing systems, does not require the integration of sensors into the structure and electrical circuits of the truck and represents a compact, autonomous device that can be located at any convenient place in the cab. In order to create such a device, it is proposed to use the magnitude of the magnetic field strength generated by DC traction motors as a signal carrying information about the mass of the transported cargo. To measure the magnetic field strength, a flux gate is used, which converts the magnitude of the magnetic field strength into the magnitude of the current. An original circuit for powering the fluxgate excitation winding using a modulated signal generator based on logic elements is proposed. The used power supply scheme allows to exclude the influence of the fluxgate excitation winding on the generator frequency, as well as to increase the fluxgate sensitivity, which makes it possible to install the sensor in any convenient place in the dump truck cabin, and not in the immediate vicinity of the traction motors.

Electro-Magnetic and Structural Analysis of Six-Pole Hybrid-Excited Permanent Magnet Motors

Potentials and limits of the Hybrid-Excitation Permanent-Magnet (HEPM) synchronous machine are dealt with in this paper. A six-pole machine is taken into consideration, and both parallel and series configurations are analysed and compared. Taking advantage of the rotor excitation coils, the permanent magnet (PM) rotor flux can be adjusted according to the operating speed to improve its performance parameters. The electro-magnetic force is analysed in its first harmonic and in the complete shape. Moreover, a comparison between analytical and numerical formulation has been done for the rotor current control. In particular, the speed range is extended, and electro-mechanical torque and power are increased, as well as the efficiency. It will be shown that the rotor flux reduction by using the excitation winding yields an improvement of the motor performance. The main advantage will be obtained during the flux-weakening operations. In this paper, different rotor topologies will be analysed to highlight the advantages and drawbacks of each of them, and how it is possible to achieve higher speed with higher torque and without high saliency ratio. A magnetic network will be introduced to explain the different contribution of the excitation winding to the rotor flux. Furthermore, a comparison of the amount of the volume of PM, copper and iron in internal permanent magnet (IPM) motor and HEPM motor will be analysed. Actually, an analysis of the harmonic content in the electro-motive force even varying the excitation current and a mechanical stress analysis of each machine will be shown. Finally, it will be verified that the excitation losses represent a minimum component of the total losses.

Quantifying Hole-Edge Crack of Bolt Joints by Using an Embedding Triangle Eddy Current Sensing Film

Hole-edge crack quantification of bolt joints is critical for monitoring and estimating structural integrity of aircraft. The paper proposes a new triangle eddy current sensor array for the purpose of increasing the level of quantifying hole-edge crack parameters, especially, the crack angle. The new senor array consists of triangular coils instead of planar rectangular coils. The configuration of the novel sensor array, including the excitation current directions and the excitation winding shape, is optimized by simulation. The ability of the proposed sensing film to identify the crack parameters has been verified by finite element simulations and experiments. Results shows that triangular coils with same current directions in circumferentially adjacent coils and opposite current directions in axially adjacent coils achieve better performance in sensor linearity and resolution compared to rectangular coils. In addition, it has also been proved that the sensing film has a good potential to identify the crack depth and length.