Analysis of Coupled Thermal and Electromagnetic Processes in Linear Induction Motors Based on a Three-Dimensional Thermal Model

The article describes a mathematical model of interconnected electromechanical and thermal processes in a linear induction motor (LIM). Here, we present the structure of the thermal model and provide the calculation formulas of the model. The thermal model consisted of eight control volumes on each tooth pitch of the LIM. Moreover, we also present a model of electromechanical processes and its interaction with the thermal model. The electromechanical model was based on the detailed magnetic and electrical equivalent circuits of the LIM. Model verification was performed using a model based on the finite element method and using experimental data. We also conducted a study focused on the necessity of considering the influence of various features of the thermal processes. We herein discuss the application of the model implemented in the MATLAB/Simulink, which was used to analyze the thermal performance of linear transport and technological induction motors. For the traction single-sided linear induction motor, we determined limits of safe operation by considering the unevenness of heating along the length in two cases: natural cooling and forced cooling. For forced cooling, required values of air flow were determined. For the arc induction motor of the screw press, the influence of various factors (i.e., reduction of the stroke, the use of a soft start, and the use of a forced cooling) on heating was evaluated.

SIMULATION OF STARTING MODES OF SYNCHRONOUS ELECTRIC DRIVE OF A PUMP STATION

The article studies the starting modes of a synchronous electric drive of a pumping station, in direct and soft start of high-voltage synchronous motors of an irrigation pumping station of the first stage. The analysis of negative starting factors of synchronous machines is made on the basis of computer modeling of the research object. The simulation results are clearly shown for the main parameters of a synchronous electric drive, such as its rotation speed, stator currents, electromagnetic torque on the shaft, etc.

Analysis and Revision of Torque Formula for Hydro-viscous Clutch

Hydro-viscous clutch is a speed-regulating device for heavy fans and water pumps. It has important engineering significance in the fields of soft-start for rotating machinery. More and more attention has been paid to its torque and control characteristics. This paper is focused on the torque formula for hydro-viscous clutch (HVC), assuming that multi-friction plates distribute ununiformly with different oil film thickness. A mathematical model of friction plates was constructed, then the distribution formula of the oil film thickness was obtained. A new expression was presented using a modified factor. Parameters such as pressure, viscous torque, and oil film thickness were obtained. The results show that each clearance of friction plates is not the same and the distribution of oil film thickness is influenced by pressing force, groove depth, angular ratio of groove/non-groove, and static friction force. To verify the proposed expression, relevant experiments were carried out on an HVC with multi-friction plates, and the experimental results indicate that the new expression is more accurate compared to the original one.

THE EFFECT OF DIFFERENT LIGHT CURED UNIT INTENSITIES ON THE DEPTH OF POLYMERIZATION OF BULK FILL SCULPTABLE COMPOSITE RESIN RESTORATIONS

Background : The latest development of dental material restoration is a bulk fill sculptable composite resin. This material can be applied to a 4 mm cavity at once irradiation. The success of polymerization can be affected by improper irradiation. Both the physical and mechanical properties of the material also can be decreased by improper irradiation. This study aimed to determine the effect of different light-cured unit intensities on the depth of polymerization of bulk fills sculptable composite resin restorations.Method : This research method was an experimental analytic type of post-test only control group design laboratory, consisting of 24 bulk fill sculptable composite resin with a diameter of 4mm x 6mm thickness divided into 6 groups:A1(3M ESPE-low intensity),A2(3M ESPE-high intensity),A3(3M ESPE-soft start intensity),B1(Ivoclar vivacity-low intensity),B2(Ivoclar vivadent-high intensity) and B3(Ivoclar vivadent-soft start intensity). Result : The results showed a significant effect of the low, high, and soft start intensity light-cured units in the bulk fill sculptable composite resin groups by Kruskal-Wallis test 0.00 (p <0.05).Conclusion : The best polymerization depth of bulk fill sculptable composite resin was 3M ESPE and it was affected by the high and low-intensity light-cured units