No-load Conditions Research Articles

Detailed Controller Synthesis and Laboratory Verification of a Matching-Controlled Grid-Forming Inverter for Microgrid Applications

Grid-forming inverters are the essential components in the effort to integrate renewable energy resources into stand-alone power systems and microgrids. Performance of these inverters directly depends on their control parameters embodied in the controller. Even the most conscientiously designed controller will exhibit suboptimal performance upon implementation due to the presence of parasitic elements in the existing hardware. Hence, the controller has to be tuned and optimized. In the present article, the process of implementation, laboratory verification, and tuning of a matching-controlled grid-forming inverter is presented. In order to assess the efficiency of the grid-forming controller, its operation has been tested and analyzed in blackstart, steady state, and transient operation. For this purpose, a systematic sensitivity analysis has been conducted and the control parameters have been tuned in laboratory tests. The laboratory results verify proper operation of a 7 kW grid-forming inverter in all three test scenarios. After applying the proposed method on the tested grid-forming inverter in steady state operation, total harmonic distortion (THD) of the output voltage is less than 0.5% for its practical loading range (maximum THD is less than 1% in no-load condition). The system is able to blackstart and supply the loads. Finally, the studied grid-forming inverter is stable in the presence of severe step load changes and disturbances, i.e., voltage overshoot is managed well and compensated for with a low settling time using this approach.

Research on Magnetic-Thermal-Force Multi-Physical Field Coupling of a High-Frequency Transformer with Different Winding Arrangements

In order to clarify the magnetic-thermal-force changing rule of high-frequency transformers under different winding arrangements, this paper tests the magnetization and loss characteristics of nanocrystalline materials at different temperatures, and based on the magnetization and loss data, establishes a magnetic-thermal-force coupling calculation model of 15 kVA, 5 kHz nanocrystalline high-frequency transformers, and calculates and analyzes the magnetic flux density, loss and temperature rise distributions of high-frequency transformers with three different winding arrangements under no-load and short-circuit conditions, respectively. Through comparative analysis, it was found that under no-load conditions, the cross-transposition of winding has less influence on the magnetic flux of the high-frequency transformer core, but it can reduce the iron-core loss and transformer temperature rise. The cross-transposition of winding under short-circuit conditions can significantly reduce the leakage magnetic field strength of high-frequency transformers; complete cross-transposition weakens the high-frequency transformer losses and temperature rise better than partial cross-transposition. According to the winding current density and core leakage field distribution under short-circuit conditions, we calculated and analyzed the distribution of its the axial and radial electromagnetic forces. The results show that the axial electromagnetic force causes the winding to be squeezed from both ends to the middle, the radial electromagnetic force causes the primary winding to shrink inward and the secondary winding to expand outward, so cross-transposition can greatly reduce electromagnetic force and weakening the deformation of the winding. Therefore, high-frequency transformers of winding cross-transposed should be used in actual projects to reduce transformer temperature rise and improve efficiency and security. This research has theoretical significance for the multi-physical field coupling of high-frequency transformers and its structural design.

The Influence of Hydraulic Characteristics on Structural Performance in a Pump-Turbine under No-Load Conditions

The operating state of a pump-turbine unit under no-load conditions is directly related to its safe and stable operation. In order to probe into the influence of hydraulic characteristics on structural performance, a pump-turbine assembled in China is selected for research by using CFD (computational fluid dynamics) and unidirectional FSI (fluid–structure interaction) methods. The vortex distribution and the law of pressure pulsation propagation are analyzed to capture the peculiar flow phenomena. The results show that the vortex distribution in the runner channel appears initially at the suction side of the blades but then propagates toward the pressure side with GVO. This produces rotating stall frequencies (0.7fn) and a combination of the RSI, asymmetry of the water ring in vaneless space, and high-amplitude pressure pulsations in the downstream channel close to the runner inlet and elbow section of the draft tube. This, in turn, is associated with the structural stress of the runner and guide vane. The stress level of the guide vane becomes alleviated under no-load conditions with large GVO, but the stress distribution of the runner is no longer symmetrical, which aligns with the vortex evolution in the runner passage. The stress concentration that develops further along the blade root increases the structural failure, which is also captured and verified as a crack in the prototype runner. The phenomena suggest that the RPT should avoid operating under no-load conditions with large GVO as far as possible. Therefore, in the design or optimization of the pump-turbine unit, the structures of the guide vanes and runner could be treated as a whole to investigate the resulting internal flow and structure characteristics.

Enhanced Hybrid Converter Topology for PV-Grid-EV Integration

Due to the continuous price reductions in PV mod- ules and significant development in electric vehicles (EV), the integration of solar photovoltaic (PV) into the EV charging system has been inevitable. This paper proposes the control of a hybrid converter in a EV charging station. This system consists of a PV fed Enhanced Hybrid Converter (EHC) integrated with a single-phase grid. The control of the EHC to perceive maximum power from PV, dc voltage regulation for EV charging and AC power control for feeding the AC grid is presented. A testbed under different circumstances i.e., AC and DC power distribution from the solar PV under different insolation conditions, feeding PV power to grid under the absence of EV, feeding PV power to EV charging port in the absence of grid and feeding EV power to grid under the absence of PV power is developed under MATLAB/Simulink environment for validation. Also, a switching logic is proposed for the operation of the EHC converter under no-load condition. The hardware prototype is developed with TI F28379D processor in the laboratory has validated the proposed EHC on various conditions.

Load Capacity of Nickel–Metal Hydride Battery and Proton-Exchange-Membrane Fuel Cells in the Fuel-Cell-Hybrid-Electric-Vehicle Powertrain

This article investigates the impact of loading on the hybrid powertrain of the FCAT-30 model, equipped with a proton-exchange-membrane fuel cell (PEMFC) and a nickel–metal hydride (NiMH) battery. This study involves analyzing structural component performance based on voltage and current measurements of the fuel cell, battery, and powertrain. Tests conducted under different load conditions reveal significant differences in battery current and fuel-cell voltage, highlighting the crucial role of the battery in the powertrain. External loading induces cyclic operation of the fuel cell, generating peak power. The energy balance analysis demonstrates that, under no-load conditions, the vehicle consumes 37.3% of its energy from the fuel cell, with a total energy consumption of 3597 J. Under load, the energy from the battery is significantly utilized, resulting in a constant fuel-cell share of approximately 19%, regardless of the vehicle’s load. This study concludes that the battery predominantly drives the powertrain, with the fuel cell acting as a secondary energy source. These findings provide valuable insights into the power distribution and energy balance in the hybrid powertrain. Using a load driving profile reduced the fuel-cell-stack energy contribution by 6.85% relative to driving without an external load.

Stator current signal crossing for fault diagnosis of self-excited induction generators

This paper presents a novel method for modelling and diagnosis of electrical and mechanical faults in fixed-Speed Self-Excited Induction Generators (SEIGs) operating in autonomous mode in a small-scale wind energy system. The proposed method is validated using the finite element method. After the selection of the magnetising capacitors, the self-excitation process is performed under no-load conditions. Once the stator voltage is established, a symmetrical three-phase load is connected. The fault detection method introduced here is called Stator Current Signal Crossing (SCSC). The SCSC extracts a new signal from the stator currents, that enables the detection of stator inter turn shortcircuits, broken rotor bars, and dynamic eccentricity faults in SEIGs. A spectral analysis of SCSC using the Fast Fourier Transform (FFT) algorithm is used to precisely locate the induced fault components. What sets this fault-tracking method apart from its predecessors is its exceptional ability to detect faults of any magnitude by analysing the modulation of the SCSC signal. These faults are directly identified by the presence of distinct harmonics, each indicative of a specific type of fault. This study also focuses on the SEIG in a wind energy system, whereas previous works have mainly addressed the induction machine in motor mode. In contrast, previous methods involved analysing a single current signal and isolating specific harmonics from a wide frequency range. The effectiveness of the proposed fault detection method and the self-excitation process are illustrated by simulation results and spectral analysis.

Analysis Optimization and Comparison to Detect Failures in the Squirrel-Cage Rotor using High-Level Wavelets

The methods and tools used for signal analysis extracted from the induction motors, such as the motor current signature analysis (MCSA) used for data collection on a non-invasive basis, the multi-resolution analysis (MRA) and discrete wavelet transform (DWT), are efficient tools for the signal analysis at different levels or resolutions, these tools have been applied together to improve detection of failures in the rotor of induction motors in condition of no-load. This work focuses on the study of rotor cage end ring, in a condition with lower-load or no-load where uncertainty predominates, this area of study is complicated to analyze correctly with conventional methods, but in these circumstances, the analysis using TDW has better performance. The article presents an alternative way of detecting failures in three phases induction motors in no-load state method with an optimized method and a comparison between results of the analysis with two different levels of the high-order Wavelet Daubechies, studying and evaluating its performance for the detection of broken ring, all this supported with a specific signal pre-processing and post-processing to improve the results of detection in incipient faults.

Evaluation of Counter-Rotating Dual-Rotor Permanent-Magnet Flux-Switching Machine with Series and Parallel Stator Teeth

In this study, the focus is on the magnetic path formation and its effects on the performance of a counter-rotating dual-rotor permanent-magnet flux-switching machine (CR-DRPMFSM) for direct-drive counter-rotating wind power generation, based on different stator slot and rotor pole combinations. To fully exploit rotor-shaft bore and improve fault-tolerant design, as well as increase torque density, dual-rotor topologies with the capability for dual electrical and dual mechanical ports are investigated. Moreover, the direct-drive counter-rotating wind power generation technique offers a brushless topology, thus reducing maintenance cost and improving energy conversion efficiency compared to single-blade wind turbine systems. Using finite element analysis (FEA), the inherent magnetic coupling of the series and parallel paths shows varied impacts on the electromagnetic performance of four different CR-DRPMFSMs based on the slot/pole combinations (MI to MIV) considered in this study. The key electromagnetic performance indices, such as torque, cogging torque, torque ripple, power factor, and efficiency, show proportionate variation to the coupling level. A comparative analysis shows that MI exhibits higher average torque, lower torque ripples, and high efficiency, reaching 90% with a power factor of 0.6. As an optimal design, an MI test prototype is developed. The experimental test prototype validates the FEA results under no-load and on-load conditions.

Rotor Speed Analysis of SMC-based IFOC for Low-Speed Induction Motor Control

The control of electric motors, particularly three-phase induction motors, has developed rapidly due to their application in industry. Indirect Field Oriented Control (IFOC) is one of the most widely used control systems due to its ease of application. IFOC controls a three-phase induction motor in the same way as a DC motor. However, IFOC requires a Sliding Mode Control (SMC) controller with Lyapunov stability theory to ensure robustness and stability. In exceptional conditions, such as low-speed settings, the SMC-based IFOC requires unique sets to operate with a steady-state error (Ess) at a speed response of less than 2%. Other parameters to be considered are rise time and electromagnetic torque response at low speeds. The addition of the boundary layer of the hyperbolic tangent function to a first-order SMC can increase induction motor (IM) control up to 175 rpm with a value of Ess = 1.96% compared to the saturation and signum functions, which are only capable of a reference speed of 300 rpm in no-load conditions with a value of Ess = 2% for the saturation function and 1.94% for the signum function. SMC with the hyperbolic tangent function boundary layer performs best under load conditions. The rising time value does not significantly differ under no-load or torque-load conditions between the SMC with the saturation, hyperbolic tangent function boundary layers and without the boundary layer. Adding a boundary layer with the hyperbolic tangent function can reduce ripple significantly compared to the saturation function under no-load or load conditions.

Induction Motor Stator Winding Inter-Tern Short Circuit Fault Detection Based on Start-Up Current Envelope Energy.

Inter-turn short circuit (ITSC) is a common fault in induction motors. However, it is challenging to detect the early stage of ITSC fault. To address this issue, this paper proposes an ITSC fault detection method for three-phase induction motors based on start-up current envelope energy. This approach uses Akima interpolation to calculate the envelope of the measured start-up current of the induction motor. A Gaussian window weighting is applied to eliminate endpoint effects caused by the initial phase angle, and the enveloping energy is obtained using the energy formula as the fault feature. Finally, by combining this with the support vector machine (SVM) classification learner, fault detection of ITSC in induction motors is achieved. The experimental results show that the average accuracy of this method reaches 96.9%, which can quickly and accurately detect ITSC faults in asynchronous motors and determine the severity of the faults. Furthermore, the average accuracy of SVM in detecting early ITSC faults under no-load conditions is 98.8%, which is higher than other classification learners, including LR, KNN, and NN. This study provides a new idea for induction motor fault detection and can contribute to induction motor maintenance.

Valuing epistemic rationality bolsters the effect of analytic thinking on skepticism toward pseudo-profound bullshit

We examine in three studies whether skepticism toward pseudo-profound bullshit (BS) requires sufficient analytic sophistication as well as motivation to form beliefs based on logic and evidence. Across studies, the positive relationship between individual differences in cognitive sophistication and skepticism toward BS was stronger among people who ascribe high (vs. low) value to being epistemically rational. Moreover, experimentally reducing people's ability to engage in analytic thinking (by inducing cognitive load) reduced skepticism toward BS among individuals who ascribe high value to being epistemically rational. By contrast, skepticism toward BS was equally low in the no-load condition as under cognitive load among people who ascribe low value to epistemic rationality (Study 2). We also demonstrate that cognitive sophistication, coupled with ascribing high value to being epistemically rational, predicts skepticism toward BS, regardless of the source's credibility (Study 3).

Synchronous Generator Stability Characterization for Gas Power Plants Using Load Rejection Tests

For power grid operators, knowing the transient response of the synchronous generators (SGs) included in their grids is important in order to simulate and monitor faults and other contingencies. However, the time constant of the automatic voltage regulator (AVR) and speed governors of SGs are not fast enough to show their transient dynamics in the case of a fault in the grid. This paper presents a fieldwork carried out in more than 60 gas power plants, where the response of their controllers was studied. These power plants are running and supplying electricity to the Spanish grid. The study consists of recording some SG responses in different situations, varying the AVR or the speed governor setpoints while the generator is running at no-load conditions, and also performing load rejection tests, achieving a real fault emulation. Once all the data are gathered, a fitting of the SG parameters is performed by computer simulations using GENSAL, GAST and SEXS models replicating the performed field tests. This work allows us to build an accurate network model for the whole power system and check which plants are having trouble in the case of contingencies in the grid.

A Novel Analytical Formulation of the Magnetic Field Generated by Halbach Permanent Magnet Arrays

This paper presents an analytical study of the air-gap magnetic field of a surface permanent magnet (SPM) linear, slot-less machine with a Halbach PM configuration, under the no-load condition. While other analytical formulations of the magnetic field generated by PMs are available, they exhibit some drawbacks, such as only providing a Fourier series, or being suitable to determine magnetic field average values, but not local magnetic field distributions. On the contrary, the proposed approach allows the determination of a unique, closed-form formulation for the slot-less machine air-gap field. This is obtained starting from the complex expression of the magnetic field of a conductor, inside the air gap, between two parallel smooth iron surfaces, obtained by means of the method of images. The magnetic field due to an infinitesimal conductor belonging to a current sheet is then integrated along a segment, providing the expression of the magnetic field due to the corresponding linear current density distribution, for current sheets perpendicular or parallel to the iron surfaces. Any Halbach PM segment disposition can, hence, be obtained via a suitable combination of field distributions generated by couples of current sheets with perpendicular and parallel orientation. Lastly, the no-load magnetic field expression with a Halbach array of PMs is retrieved. The proposed analytical model provides an accurate representation of the magnetic field distribution produced by any Halbach array, with an arbitrary number of segments and orientations. Additionally, the results obtained from the proposed analytical expressions are compared with FEM simulations realized by commercial software, and show an excellent agreement.

Uji Performa Alat Pengering Tray Dryer Untuk Komoditas Hasil Pertanian Yang Memanfaatkan Kalor Buangan Kondensor Mesin Pengkondisian Udara (Air Conditioning) Domestik

The drying methods currently used by farmers still rely heavily on direct solar power, so that the continuity of drying to reduce water content cannot be controlled properly, which has a direct impact on the low quantity and quality of drying results, as well as poor product hygiene. Utilization of condenser waste heat from cooling machines is one of the development applications for heat pump systems. The advantages of heat pumps for the drying process include their ability to control the temperature and humidity in the drying chamber, so that they can be adjusted for various drying conditions and the drying process is more efficient and environmentally friendly. This research aims to determine the performance of drying machines for agricultural commodities (cocoa beans) using the method of developing a domestic air conditioning machine, by adding a condenser arranged in series with the main condenser to function as a drying chamber. The results of the modification of this tool consist of five main parts, namely the compressor, tray dryer room (additional condenser), main condenser, expansion valve, and evaporator. Testing of this dryer was carried out with two types of experiments, namely experiments without load and experiments with load. The test was carried out at the maximum working time of the condenser by setting the lowest working evaporator, namely 16°C. The lower the working temperature of the evaporator, the higher the working temperature of condenser 1. This is done to get maximum work from this modified dryer. Based on tests for temperature and relative humidity (RH) under load and no-load conditions, the values are not too different. After approximately 2 hours of operation or when the machine was working in steady state, the highest temperature was obtained at 87°C while the highest average RH was obtained at 78% in the drying rack space. The performance of this agricultural commodity drying machine has functioned well, especially for cocoa beans which have been dried to a standard moisture content of 7.5% in accordance with SNI 2322-2008 for an operating time of 130 minutes. The dryer system by utilizing exhaust heat from the condenser in this domestic air conditioning machine can work well without reducing its main function as indicated by the maximum temperature value of 20oC around the evaporator.Â

Analysis of the Magneto-Thermal Bidirectional Coupling Strength of Macro and Micro Integration for Self-Starting Permanent Magnet Hysteresis Synchronous Motors

High-speed permanent magnet synchronous motors (PMSMs) are usually started with the hybrid low-speed open-loop and high-speed closed-loop control mode. However, low-speed open-loop control produces large starting current, or even current overload, resulting in demagnetization and motor damage. Therefore, there is an urgent need to develop a high-speed permanent magnet synchronous motor with self-starting ability at low speed, that is, a permanent magnet hysteresis motor (PMHM). This paper takes the permanent magnet ring hysteresis column rotor structure as the research object. Firstly, the performance of this type of rotor is improved using the micro level of effective layer material AlNiCo, and the mechanical properties of AlNiCo are calculated. Secondly, based on the thick-walled cylinder theory, the analytical model for calculating the strength of the composite rotor considering the temperature effect is deduced, and the tangential and radial stress distribution for each part of the rotor under no-load and load conditions are obtained. Then, the electromagnetic losses and temperature field distribution of the rotor are obtained using the magneto-thermal bidirectional coupling finite element method. Finally, strength of the thermal rotor is analyzed by substituting the temperature rise curve function and AlNiCo parameters at the operating temperature. The comparison of the stress calculation results of the semi-analytical solution and the finite element method showed that the error between both of them is less than 5%, which verified that the semi-analytical solution can accurately analyze the thermal stress distribution of the rotor during high-speed rotation.

Transient-steady state vibration characteristics and influencing factors under no-load closing conditions of converter transformers

The converter transformer plays a key role in the HVDC transmission project. It will be put back into the power grid after a power outage for maintenance. The transient overvoltage and excitation inrush current during charging and closing will cause shock vibration and affect the stability of the internal mechanical structure. In addition, the on-load tap-changer (OLTC) shifting operation after closing will also lead to changes in the vibration characteristics. Because of insufficient research on vibration during closing transient and no-load operation, this paper measures the transient vibration change process during no-load closing and tap-changer action in a ± 800 kV converter station. Furthermore, the influence of voltage and winding turns changes on no-load vibration is also analyzed, and multi-characteristic parameters of vibration impulse factor, offset factor, and odd–even harmonic ratio are extracted to realize no-load state identification. The results show that the no-load vibration increases with the increase of the voltage, and decreases with the increase of the number of turns of the grid-side winding. More importantly, both the charging closing and the tap-changer action will produce vibration and shock components, and the maximum transient vibration exceeds 90 m/s2, which is 35.7 times that of the steady-state. Odd harmonic components of 50 Hz, such as 150 Hz, 250 Hz, etc., will appear in the vibration spectrum under the action of the 2nd, 4th, and other even harmonics in the excitation inrush current. While the non-excitation inrush current is mainly an even multiple of 50 Hz. The research results reveal the vibration characteristics of the converter transformer during closing transient and no-load operation, and provide a theoretical reference for the evaluation and identification of the converter transformer under all operating conditions.

A Transient Seepage–Thermal Stability Model for Cohesionless Soil Slopes in the Semi-Arid Continental Climate of the Canadian Prairies

Seasonal weather variations have a profound effect on the integrity of cohesionless soil slopes in the Canadian Prairies owing to the prevalent semi-arid continental climate. The primary contribution of this research is the development of a transient and two-dimensional stability model that is fully coupled with hydraulic and thermal flows. The model was used to predict the factor of safety (FS) for two slope geometries (18 m height and 26 m height) subjected to three weather scenarios (mean, extreme wet, and extreme dry) and four ponding combinations on the upstream and downstream sides of the slopes under no-load and train-load conditions. Results indicated that for mean climate conditions, FS trends fluctuate till April, followed by an increase that remains constant up to November and decreases thereafter. Generally, the FS shows subdued fluctuations and higher values for the high slope compared with the low slope. For wet climate conditions, the FS patterns are similar to mean conditions, albeit with reduced durations of stability during summer. For dry climate conditions, FS values are higher than mean conditions and nearly constant for most of the year. For no ponding and downstream ponding, FS > 1 throughout the year. In contrast, FS > 1 only during the summer (with reduced time in wet climate and extended time in dry climate conditions) for upstream ponding and upstream–downstream ponding. For train loading, FS shows subdued fluctuations and lower values than the corresponding no-loading scenarios for both slopes. The effects of climate conditions and ponding scenarios are further reduced for the high slope. These findings are useful for decision making with regard to the initial design and ongoing performance of natural slopes and embankments in the cohesionless soils of the region.

Extensive analysis of PCM-based heat sink with different fin arrangements under varying load conditions and variable aspect ratio

The present study compares a modified variable height fin heat sink with the conventional constant height fin heat sink. The two heat sinks are filled with an equal volume of PCM (n-eicosane) and a fin volume fraction of 8 %. The experiments are performed for constant loads and also different power surge conditions. The pulsed heat loads are applied for two scenarios: 1. Constant load 4 W - power surge and constant load 4 W - power surge - 1800 s no-load condition, and 2. Power surge (50 s, 100 s, and 150 s) - no-load conditions of 1800 s. During experiments, the proposed variable height fin heat sinks possess better thermal performance for all load scenarios. Further, a 3D computational model is developed using ANSYS Fluent 19 to assess not only the effect of fin arrangement for different aspect ratios but also the impact of fin shape. The enclosure aspect ratio employed for the given study ranges from 0.3 to 0.8 for both the heat sinks. Regarding the fin structure in a heat sink, four types of fin shapes are adopted: square, circular, diamond, and triangular. The contour images of temperature and the liquid fraction are shown for the charging process. For the discharging process, the time required for the heat sinks to completely solidify the PCM is discussed. From the outcomes, variable height fin heat sinks provide enhanced melting/solidification for all the aspect ratios and fin shapes considered. As the aspect ratio increases, the time difference between the heat sink for the completion of the discharging cycle is reduced. Moreover, the triangular shaped fin shows a higher enhancement percentage of 2.29 % and 1.43 % during melting and 6.25 % and 12.5 % during solidification for both the heat sinks, respectively.

Numerical and experimental study of a very low head (VLH) turbine in an open channel at no-load conditions

Very low head (VLH) turbines are axial turbines with the capability of extracting power at a high efficiency of over 80% from very low heads (less than 4.5 m) and high flow rates of up to 30 m3/s per unit, with a significant reduction in construction costs, compared to conventional hydropower turbines. At no-load conditions, the turbine reaches its runaway speed, which is its theoretical maximum speed, causing damage to the equipment and the turbine structure, thereby imposing a considerable financial burden. As a result, understanding the performance of the turbine at the runaway speed is of utmost importance. The present paper centers its experimental and simulation efforts on predicting the runaway speed of the turbine rotor. An experimental study is conducted to determine the relationship between the runaway speed of the turbine and the flow rate, as well as compare its value with the rotational speed at the design point. Through the conducted experiments, it has been observed that at the mass flow rate corresponding to the design point, the runaway speed is 2.12 times higher than the rated value. Transient simulations using Computational Fluid Dynamics (CFD) are employed to investigate the performance under no-load conditions by estimating the generated torque as a key parameter. Simulations are carried out in an open channel configuration using the Ansys CFX software, and the results are compared to the experiments. In this study, a portion of the work focuses on simulating the free surface flow over the turbine, which allows for more realistic simulations of the turbine's operational behavior. The results of these simulations indicate that the homogeneous model is able to correctly predict free surface flow downstream and upstream. The numerical approach can also predict the runaway state of the VLH turbine with high accuracy, exceeding 95%; however, this variation is due to mechanical and hydraulic losses that have not been factored into the simulation. In this CFD modeling, setting up the boundary conditions accurately is vital, especially for the water levels at the inlet and outlet.

Core Loss Equivalent Resistance Modeling of Small- and Medium-Sized Converter-Fed Induction Motors Considering Supply and Spatial Harmonics

In order to estimate the core loss resistance of converter-fed induction motor accurately and efficiently, an analytical piecewise variable-coefficient core loss model is proposed. By introducing two voltage harmonics related coefficients, the influence of converter harmonics on core loss is simply and effectively considered. In addition, the surface and pulse loss caused by slot harmonics and the additional harmonic core loss caused by harmonic magnetic potential of stator winding under load condition are also considered. Based on the proposed model, an advanced core loss equivalent resistance model of converter-fed induction motor considering supply and spatial harmonics is proposed. The effectiveness of the proposed model is validated by comparisons with the measured core losses of 5.5 kW induction motor under no-load condition. In addition, compared with the finite element method under load condition, the proposed analytical model reduces the computational time significantly while maintaining high accuracy.