• Journal of Power Electronics
• /
• v.12 no.2
• /
• pp.305-316
• /
• 2012

The paper presents an accurate loss model based controller of an induction motor to calculate the optimal air gap flux. The model includes copper losses, iron losses, harmonic losses, friction and windage losses, and stray losses. These losses are represented as a function of the air gap flux. By using the calculated optimal air gap flux compared with rated flux for speed sensorless indirect vector controlled induction motor, an improvement in motor efficiency is achieved. The motor speed performance is improved using a fuzzy logic speed controller instead of a PI controller. The fuzzy logic speed controller was simulated using the fuzzy control interface block of MATLAB/SIMULINK program. The control algorithm is experimentally tested within a PC under RTAI-Linux. The simulation and experimental results show the improvement in motor efficiency and speed performance.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.5B no.4
• /
• pp.299-305
• /
• 2005

The work described in this paper is to investigate the additional iron losses and consequent temperatures in core ends of a turbo-generator wound with high voltage cables. Electromagnetic calculations are made with 3D FE models, which include the lamination material with anisotropic properties both in magnetic permeability and electric conductivity. The models also include the geometry of the stator teeth and eventually the axial steps designated to reduce the core end losses. The 3D model of the rotor consists of field windings with straight in-slot parts and end windings. The thermal models are simplified into two dimensions and include the heat sources dumped from the 3D electromagnetic solutions. The influences of power factor on additional iron losses are studied for this cable wound machine and conventional machines. The calculation results show that the additional iron losses can be reduced to about $15\%$ by introducing some small steps around the airgap corner of core ends.

• Proceedings of the KIEE Conference
• /
• 2006.07b
• /
• pp.901-902
• /
• 2006

In high-speed PM machines, rotor losses form a larger proportion of the total losses than usual in conventional low speed machines. In order to maintain the mechanical integrity of a high-speed PM rotor intended for high-speed operation, the rotor assembly is often retained within a sleeve or can. The sleeve is exposed to field produced by the stator from either the slotting or the mmf harmonics that are not synchronous with the rotor. These non-synchronous fields cause the significant rotor losses. An optimum design of high-speed PM machines requires the accurate prediction for these rotor losses. On the basis of analytical field analysis and 2D finite element analysis (FEA), this paper deals with the rotor losses.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.42
• /
• pp.38-49
• /
• 2000

Two application rates (9 and 18 t/ha) of poultry litter and a recommended rate of commercial fertilizer were studied to determine their effects on nutrient (N and P) losses in surface and subsurface runoff and loadings in soil layers from conventionally-tilled com by the treatments. The model predicted higher sediment losses than observed data from all treatments. The overpredicted sediment losses resulted in overprediction of organic-N and sediment-P losses in surface runoff. Simulated soluble-P losses in surface runoff were close to observed data, while NO3-N losses in surface runoff were underpredicted from all treatments. Observed NO3-N concentrations in leachate at 1.0-m depth from commercial fertilizer treatment were fairly well predicted. But the concentratins were overpredicted from poultry litter treatments due to high simulation of organic-N mineralization simulated by the model.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.53 no.7
• /
• pp.437-443
• /
• 2004

In this work the AC loss measurement setup based on an iron core background magnet, not used in a conventional one, has been successfully developed. To prove its validity, a round-robin test for the same Bi-2223 tape sample among three institutes has been done. The results show that the self-field and magnetization losses from the developed setup well agree with the losses measured at two other institutes of Korea Basic Science Institute and Yokohama National University. The measured magnetization losses for parallel or perpendicular fields can be well predicted from the slab model or the strip model for a filamentary region. However the magnetization losses for longitudinal fields can be rather predicted by the slab model for a decoupled filament. The self-field losses are well explained by the Norris ellipse model.

• Proceedings of the KIEE Conference
• /
• 1999.07a
• /
• pp.342-344
• /
• 1999

This paper presents the analysis of core losses in capacitor-run single phase induction motors using the finite element methods. The double revolving field theory can be used for the analysis to assess the quantitative and qualitative performance of the single-phase induction motor. But it is difficult to evaluate accurately the core losses. It is more difficult to segregate stator and rotor core losses at no-load and load conditions. Numerical analysis such as FEM can be used effectively for the accurate calculation of core losses and motors performances. In this paper, the coupling method of core loss characteristic equation and FEM are proposed for the accurate calculation of core losses in the stator and rotor. The FFT is also used to calculate fundamental and harmonic components in the yoke and teeth parts of motor.

• International Journal of Fluid Machinery and Systems
• /
• v.3 no.4
• /
• pp.279-284
• /
• 2010

Tip clearance losses occur in every turbomachine. To estimate the losses in efficiency it is important to understand the mechanism of this secondary flow. Tip clearance losses are mainly caused by a spiral vortex formed on the suction side of the blade of a turbomachine, which induces a drag and also has an influence on the incident flow of the blades. In this paper a physical based scaling method is developed out of an analytical ansatz for the tip clearance losses. This scaling method is validated by measurements on an axial fan with five different tip clearances.

• Journal of Power Electronics
• /
• v.17 no.6
• /
• pp.1490-1499
• /
• 2017

The modular multilevel converter (MMC) is generally considered to be a promising topology for medium-voltage and high-voltage applications. However, in order to apply it to high-power applications, a huge number of switching devices is essential. The numerous switching devices lead to considerable switching losses, high cost and a larger heat sink for each of the switching device. In order to reduce the switching losses of a MMC, this paper analyzes the performance of the conventional discontinuous pulse-width modulation (DPWM) method and its efficiency. In addition, it proposes a modified novel DPWM method for advanced switching losses reduction. The novel DPWM scheme includes an additional rotation method for voltage-balancing and power distribution among sub modules (SMs). Simulation and experimental results verify the effectiveness and performance of the proposed modulation method in terms of its switching losses reduction capability.

• Journal of Magnetics
• /
• v.16 no.1
• /
• pp.64-70
• /
• 2011

Surface-mounted permanent magnet (PM) machines were examined experimentally and theoretically, through power loss measurements and calculations. Windage, friction and copper losses were calculated using simple analytical equations and finite element (FE) analyses. Stator core losses were calculated by determining core loss coefficients through curve-fitting and magnetic behavior analysis through non-linear FE calculations. Rotor eddy current losses were calculated using FE analyses that considered the time harmonics of phase current according to load. Core, windage and friction open-circuit losses and copper loss were determined experimentally to test the validity of the analyses.

• SUVANNABHUMI
• /
• v.15 no.2
• /
• pp.131-152
• /
• 2023

In analyzing the Chinese diaspora, this paper explores losses that are encountered within the family in the nation. It argues that increased social and spatial mobilities that contribute to losses can be reconfigured through the productive lens of supermobility, as Laurence J. C. Ma conceptualizes it. Supermobile identities are significant avenues to consider the way that losses traditionally associated with migration and assimilation are revisited in view of new flows of migration and identification. In examining K. H. Lim's debut novel Written in Black (2014), this study addresses pathways from debilitating losses to productive losses journeyed by the family from the child's perspective. It offers a critical analysis of the Anglophone Bruneian novel in terms of its exclusive portrayal of an ethnic Chinese family. Departing from a fixed notion of home as cultural and physical rootedness, it explores flexible identities that are tied to shifting concepts of belonging. Rather than a magnification of social and spatial losses, the analysis highlights the way that the literary imagination of ethnic Chinese in Brunei Darussalam accommodates progressive ideas of the agency and advancement of the Chinese diaspora as a supermobile community.