Current Issue : April-June Volume : 2024 Issue Number : 2 Articles : 5 Articles
Compared to the conventional finite control set model predictive control (FCS-MPC), the double vector model predictive current control (DVMPCC) for permanent magnet synchronous motors (PMSMs) has a better steady-state performance without significantly increasing the switching frequency. However, determining optimal vectors with their dwell times requires a high computational burden. A low-complexity DVMPCC in the steady state was proposed in this study to address this problem. Firstly, the operating state of the motor was judged according to the speed error. During steady-state operation, the first optimal active vector was selected from three candidate vectors adjacent or identical to the active vector applied in the previous control period, reducing the number of comparisons by half. Next, the second optimal vector was selected from the other two active vectors, and the zero vector, the second optimal vector with the duty cycle, was determined according to the deadbeat condition of the q-axis current and cost function minimization. Finally, simulation and experimental results proved that the proposed low-complexity DVMPCC for surface-mounted permanent magnet synchronous motors is practical and feasible....
This paper investigates the current sink capacitor technique as a method to minimize the turn-off power losses of SiC MOSFETs operated with zero-voltage switching (ZVS). The method is simple and is based on adding auxiliary capacitors in parallel to the transistors, allowing the sink capacitor to take over part of the channel current, thus limiting the power loss while also advantageously lowering the dvds/dt ratio. The technique is validated and experimentally studied based on a single-pulse test setup with 1200 V-rated SiC MOSFETs, with several capacitances and gate resistance values, at various switched currents up to roughly 60 A. It is shown that by employing even very small capacitances, in the range of nanofarads, the turn-off power loss can be reduced by over tenfold, with a negligible impact on the volume and complexity of the system. Thus, the presented method can be effectively employed to improve soft-switched power converters....
Induction motors are a significant consumer of electricity. Therefore, their energy efficiency level plays a vital role in the world’s energy balance. The world’s markets strive to produce motors of efficiency class IE3 or IE4 while maximizing the use of wire and magnetic materials. However, high induction values in the motor core can also lead to significant losses in construction materials, especially in the magnetic motor housing. This article aimed to show how it is possible to determine the distribution of the magnetic field and additional losses in the yoke and the cast-iron motor frame using field-circuit methods to model the motor and to refine the analytical method for calculating these losses at the motor design stage....
This research examines how fluid damping loss affects the operation of a two-pole, 5.5 HP (4 kW) induction machine (IM) within the context of different slot opening configurations developed for downhole water pump applications. Since these motors operate with their cavities filled with fluid, the variations in fluid viscosity and density, compared to air, result in the occurrence of damping losses. Furthermore, this loss can be attributed to the motor’s stator and rotor surface geometry, as the liquid within the motor cavity moves unrestrictedly within the motor housing. This study involves the examination of the damping loss in a 24-slot IM under different stator slot indentations. The investigation utilizes computational fluid dynamics (CFD) finite element analysis (FEA) and is subsequently validated through experiments. The aim of this work is to emphasize the significance of fluid damping loss in submerged machines. Results reveal that the damping loss exceeds 8% of the motor output power when the stator surface has indentations, and it diminishes to 3.2% of the output power when a custom wedge structure is employed to eliminate these surface indentations....
In some power systems, the voltage waveform contains frequency components less than fundamental, called subharmonics or subsynchronous interharmonics. Voltage subharmonics can be both positive- and negative-sequence, independent of their frequency (order). Subharmonics exert harmful effects on sundry electrical equipment, especially on rotating machinery; they cause various noxious phenomena, such as a local saturation of the magnetic circuit, increases in power losses and windings temperature, and torque pulsations leading to vibration of unacceptable severity. Notably, previous works reported excessive vibration of rotating machinery only under no-load, while under full load, rather moderate vibration occurred. This study deals with vibration analysis of a line-start permanent magnet synchronous motor (LSPMSM) supplied with the voltage containing negative-sentence subharmonics. Experimental investigations were conducted for a 3 kW, four-pole production LSPMSM for subharmonics of various values and frequencies. Voltage subharmonics of values significantly less than reported in real power systems were found to cause unacceptable vibration, especially under full load....
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