Rated Load Conditions Research Articles

Evaluation of a\xa0newly proposed indirect efficiency determination method for permanent magnet synchronous machines

This paper evaluates the applicability of a newly proposed method for the indirect efficiency determination of permanent magnet synchronous machines by measuring individual losses. Similar methods are well-known and standardized for other kinds of electrical machines, but for permanent magnet synchronous machines, only the direct measurement of input and output power is standardized for efficiency determination according to IEC 60034-2‑1. Measurements and finite element simulations are carried out for four selected test machines with a rated power range between 45 kW and 90 kW and with different stator and rotor topologies. It is shown that the proposed method is well applicable for permanent magnet synchronous machines with a distributed integer-slot stator winding. For machine designs with more rotor losses such as motors with tooth coil windings and open stator slots, larger deviations between the direct and indirect efficiency values of up to one percentage point are determined at rated load conditions.

Effectiveness of Ethyl Acetate, 1-Octanol, and Soy Biodiesel in Stabilizing Ethanol–Diesel Fuel Blends and Performance of Compression Ignition Engine on Stabilized Fuel Blends

A study was conducted to evaluate ethyl acetate, soy biodiesel, and 1-octanol as surfactants for stabilization of ethanol–diesel fuel blends. The evaluation was based on the temperature stability and engine performance of ethanol–diesel fuel blends stabilized by selected surfactants. Among the three selected surfactants, 1-octanol was most effective in stabilizing ethanol–diesel fuel blends. Out of 20 ethanol–diesel fuel blends prepared with 1-octanol as surfactant, only 3 blends showed distinct phase separation; the rest 17 remained stable in the entire temperature range of 0–45 °C. At the rated engine speed, eight ethanol–diesel fuel blends showed similar power-producing capability as that of diesel. The engine running on diesel developed a power of 3.71 kW, while the engine brake power with ethanol–diesel fuel blends was in the range of 3.67–3.74 kW at the rated load condition. The tested fuel blends resulted in slightly higher fuel consumption and increased emission of unburnt hydrocarbons as compared to the diesel fuel. The tested fuel blends had comparable thermal efficiency and acceptable UBHC and NOx emissions compared to diesel.

Calculation and analysis of landing double rocker arms holding pole based on finite element simulation

Landing double rocker arms holding pole are widely used in the erection of UHV construction towers. Most of the construction arms are based on experience in engineering application, and there are some potential safety hazards. In this paper, the finite element model is established based on the relevant parameters of 700×700mm2 double rocker arm holding pole, and the actual lifting conditions of the pole are analysed. The finite element method is used to simulate nine working conditions for stress analysis. The results show that the double rocker arm holding pole has good mechanical properties under rated load conditions, which verifies the reliability of the arm design. Asymmetric moment hoisting is an important factor threatening the safety of holding pole, which must be strictly controlled.

Design of a Low-Power Direct-on-Line Synchronous Reluctance Motor Based on the Modified Natural Flux Line Curve Approach

A direct-on-line synchronous reluctance motor (DOLSynRM) with a rotor topology defined by the natural flux line curve approach is studied as an alternative to an induction motor (IM) using a 1.5 kW, 50 Hz synchronous reluctance motor as an example. If an IM stator is used, a direct squirrel cage rotor replacement by a synchronous reluctance rotor equipped with a damper winding might not guarantee a sufficient starting performance. To ensure the strong enough starting capability, the natural flux line curve approach was modified in the motor design. The proposed approach was applied in the optimization of the DOLSynRM using a genetic algorithm. The optimization results show a clear tendency in the rotor design when trying to achieve a reliable starting capability and to maximize the steady-state performance of the DOLSynRM. Both the stator design and the rotor diameter of the optimized DOLSynRM are different from those of a corresponding squirrel cage IM. A DOLSynRM prototype was built and tested. It showed about a 5.4%-unit higher efficiency than the original prototype IM and acceptable starting performance under the rated load condition. The starting capabilities of the motors under study are considered with different loads. The locked rotor apparent power and current stay below permissible limits in both the IM and the DOLSynRM.

A Self-Compensated Planar Coil With Integrated Single-Switch Regulator for Wireless Power Transfer (WPT) Systems

In the receiver-side (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</sub> ) of the wireless power transfer (WPT) system, the R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</sub> is composed of compensation capacitors, a rectifier stage, and a dc/dc stage. Among them, the compensation capacitors are an essential component to minimize reactive power. Also, the dc/dc stage is an inevitable component to supply a stable output to the battery. However, to meet these aforementioned unavoidable requirements, a large number of components are required in R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</sub> of the WPT system, which increases the overall system size and cost. To relieve these drawbacks, a self-compensated planar coil with integrated single-switch regulator for the WPT system is proposed in this letter. The proposed converter can remove the many number of compensation capacitors by utilizing the intrinsic capacitance between adjacent layers of the planar coil as a self-compensated factor. Moreover, by integrating a single-switch into the rectifier stage, it is possible to supply a stable output to the battery with only a single power stage and low cost. Besides, the proposed structure can obtain reduced switching loss by securing the soft-switching operation under the rated load condition. The effectiveness of the proposed structure is verified experimentally by a prototype under 150 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">V_DC</i> input and 60 W/33 V output.

Fully-integrated DCDC buck converter based on PID algorithm

With the continuous development of power supply technology, the application of power management chips becomes more extensive, and the requirements for fully integrated power management chips are getting higher. This paper designs a buck converter with a fully integrated digital control circuit and power circuit with an output voltage of 2V. In voltage mode, digital pulse width modulation (DPWM) technology and PID algorithm are used, and a digital closed-loop control buck circuit system is designed by cadence tools. The performance of analog and digital closed-loop control circuits is compared at the same buck power stage. Under rated load conditions, the lock-up time of the digital control buck circuit is 826us, the output voltage ripple is 14.75mV, the response time of load sudden change at light load is about 900us, and the response time of load sudden change at heavy load is about 2ms.

Single Input Single Output Two Level Isolated Dc-Dc Converter With Secondary Side Phase Shifting For Solar Applications

The isolated dc–dc converters with primary-side phase shifting (PPS) provides severely narrow soft-switching range for main devices in the primary side leg of full bridge converter. The leakage inductance of the high frequency transformer should be large enough for providing the energy needed for soft switching operations and also the idling power loss due to circulating current in the converter legs under large phase-shift angle, which makes reduction of conversion efficiency and complicated in designing the parameters of transformer. Furthermore, the turn-off diode commutations in the output-side rectifier are performed by hard-switching mode. To overcome all these drawbacks, a secondary side phase shifting (SPS) technique has been developed for two-level isolated DC-DC converter. This scheme provides wider soft switching range and reduced power loss due to elimination of circulating current in the primary side of high frequency transformer. In addition, SPS control also provide no reverse recovery current in diodes and hence no power losses in the secondary rectifier circuit. The control switches operate under soft switching even under rated load and short circuit conditions.&#x0D;

Adaptive Switching Frequency Selection Based on Two-Step Efficiency Optimization for Grid-Connected Inverters

A two-step efficiency optimization of a three-phase voltage source inverter with series R damped LCL filter is proposed. The first optimization step aims to find the optimal parameters of the series R damped LCL filter at rated load conditions. The objective function of step-one is to minimize the values of the passive elements of the filter-stage. Afterward, the magnetic cores of inductors are thoroughly designed using soft magnetic powder materials. This design is proposed to specify the smallest core-size required based on the value of the inductance found in step-one of the optimization. The second optimization step aims to optimally select the switching frequency of the inverter-stage considering load variations. This optimization is based on the optimized filter-stage parameters. The proposed objective function of step-two aims to minimize the power losses in the inverter-stage and filter-stage while limiting the harmonic-levels at the point of common coupling. Detailed loss-formulation including filter-stage core and copper losses is thoroughly presented. Teaching-learning-based optimization algorithm is adopted to perform the optimization problem. Experiment and simulation are done to justify the proposed optimization procedure.

Ефективність нового екранування крайніх пакетів осердя статора потужного турбогенератора

On the basis of complex research the electromagnetic and heat processes by means of mathematical and physical simulation, the efficiency for a new constructive solution of stator core end zone of powerful turbogenerator is proved. A design that allows maximum reducing temperature of the stator end packet is proposed. In order to increase reliability of experimental data obtained with the help of scale physical model, as well as testing of constructed mathematical model, using the latest one “adjusted” to physical model, the numerous experiments for studying effectiveness of a tooth-slot configuration shields were carried out. The small difference of magnetic flux density values obtained by means of mathematical simulation from the experimental ones allows drawing a conclusion about the reliability of result. It is shown that use of physical simulation permits investigate the appropriateness of electromagnetic field distribution without exact quantitative indices of parameters and can be applied to research the quality comparison under certain changes of model. When constructing a mathematical model, an approach was used with the help of a consecutive logic transition from a simple model of machine central part to more difficult one of end zone, using the previous results in next allows obtaining the temperature distribution in difficult areas. The heat calculation for rated load condition of turbogenerator type TGV-500 with the help of mathematical model as well as comparison of these results with experimental data for a real generator analogous type and power are made. The differences of calculated and experimental values not exceed 7%. All data obtained by means of both simulation and natural experiment are corresponded to the same turbogenerator that in total makes reliability results of mathematical simulation not obtained in a real object by various reasons of objective and subjective nature.

Evaluation of the fatigue life of a tractor’s transmission spiral bevel gear

Conventional tractor transmission spiral bevel gears are designed and evaluated based on the engine rated load, which is significantly higher than the load conditions in the field. In this study, the fatigue life of a spiral bevel gear is evaluated to obtain data for design optimization. The equivalent load was calculated using the field load data, and the integrated equivalent load was calculated based on the annual usage of major field operations in Korea. The fatigue life of three spiral bevel gear samples was evaluated using the accelerated life test (ALT) under an engine rated load condition of 120%. It was also evaluated under engine rated, plow equivalent, and integrated equivalent load. Fatigue life was estimated using the ALT results and the fatigue damage exponent based on the ALT equation. We observed that the fatigue life of the spiral bevel gear under the plow equivalent and integrated equivalent loads is higher than that under the rated load by 214 and 9,400 times, respectively. The results of this study can provide useful information for the design optimization of tractor transmission spiral bevel gears considering the field equivalent load.

Electromagnetic Performance and Diagnosis of Induction Motors With Stator Interturn Fault

Interturn fault (ITF), a common fault type of induction motors, can impact the safe and stable operation of the motor. Variations of magnetic field distribution and short circuit (SC) current were analyzed, and a diagnosis method of ITF was proposed based on the stator current complex component. First, a 1.1 kW squirrel cage induction motor whose stator winding coils were rewound was taken as a prototype. The distributions of magnetic fields before and after the fault were obtained by calculating the finite element model. Based on the simulation and experimental results under no-load, light load, and rated load conditions, the phase current and SC loop current variations were obtained under different fault degrees. Then, the variations of current amplitudes in the faulty phase, nonfaulty phases, and SC loop were analyzed to determine the impact on the operation of the motor caused by the fault. Finally, a diagnosis method of ITF, which uses the current complex component to represent the current variation, was proposed based on the calculation and analysis of faulty-motor current. The results show that this method can diagnose and locate faults effectively, verify the robustness of load variations, and provide a reference for the research on ITF of induction motors.

Comparison of Electromagnetic Performance of 10-MW HTS Double-Stator Flux Modulation Wind Generators With Different Topologies

For conventional HTS synchronous generator, the superconducting (SC) field windings or armature windings are rotating, which could complicate their industrial feasibility for the offshore wind generation. In order to overcome this drawback, a kind of HTS double-stator flux modulation generator (HTS-DSFMG) without rotating windings is proposed. This paper compares the electromagnetic performance of 10-MW HTS double-stator flux modulation generators with two different topologies, i.e., iron-cored stators with both field and armature coils, air-cored stator with field windings and iron-cored stator with armature windings. In addition, the system comparison of HTS-DSFMG with conventional HTS synchronous machine is conducted under the no-load, rated load and short-circuit fault conditions. It is found that the proposed machine can dramatically reduce the peak current and peak torque during a symmetrical three-phase short-circuit fault, and its active material mass and cost are comparable with the synchronous one under rated load condition. Finally, the ac losses analysis of the SC coils for HTS-DSFMGs is conducted and three effective methods are proposed to reduce the ac losses.

Design and Analysis of a Static Excitation Part of a Brushless Wound Rotor Excitation Synchronous Machine Without an Exciter

The static excitation part of a brushless wound rotor hybrid excitation generator without an exciter (brushless WRHEG) is analyzed in this paper. The DC stator excitation windings and rotor harmonic coils are placed in the iron core as the excitation part, so that the brushless excitation for a wound rotor hybrid excitation generator (WRHEG) can be realized. In this study, the selection of stator excitation windings and rotor harmonic coils, which are essential for achieving of the brushless excitation, is providing. The effect of the static magnetic field on the air-gap magnetic field is studied theoretically. The harmonic content of the air-gap magnetic field is analyzed by Fourier series form and the effect of harmonics on the output voltage is also investigated. The influence of the static excitation field on the iron loss is also considered. A 1.5 kVA prototype is fabricated to verify the validity of the theoretical and Finite Element (FE) analysis. The output voltage under the no-load and the rated load conditions are measured. The field regulation capacity and the efficiency of the brushless WRHEG are tested. It shows that the brushless excitation is achieved by remaining the operating performance of WRHEG unchanged.

Scalable Modeling Approach and Robust Hardware-in-the-Loop Testing of an Optimized Interleaved Bidirectional HV DC/DC Converter for Electric Vehicle Drivetrains

Automotive Original Equipment Manufacturers (OEMs) require varying levels of functionalities and model details at different phases of the electric vehicles (EV) development process, with a trade-off between accuracy and execution time. This article proposes a scalable modelling approach depending on the multi-objective targets between model functionalities, accuracy and execution time. In this article, four different fidelity levels of modelling approaches are described based on the model functionalities, accuracy and execution time. The highest error observed between the low fidelity (LoFi) map-based model and the high fidelity (HiFi) physics-based model is 5.04%; while, the simulation time of the LoFi model is ~10 4 times faster than corresponding one of the HiFi model. A detailed comparison of all characteristics between multi-fidelity models is demonstrated in this paper. Furthermore, a dSPACE SCALEXIO Hardware-in-the-Loop (HiL) testbench, equipped with a minimal latency of 18 μ sec, is used for real-time (RT) model implementation of the EV's HV DC/DC converter. The performance of the entire HiL setup is compared with the Model-in-the-Loop (MiL) setup and the highest RMSE is limited to 0.54 among the HiL and MiL results. Moreover, the accuracy (95.7%) of the passive component loss estimation is verified through the Finite Element Method (FEM) software model. Finally, the experimental results of a full-scale 30-kW SiC DC/DC converter prototype are presented to validate the accuracy and correlation between multi-fidelity models. It has been observed that the efficiency deviation between the hardware prototype and multi-fidelity models is less than 1.25% at full load. Furthermore, the SiC Interleaved Bidirectional Converter (IBC) prototype achieves a high efficiency of 98.4% at rated load condition.

Effect of part load operating conditions of an air conditioner on the number of refrigerant paths and heat transfer performance of a condenser

Heat exchangers for heat pump condensers and evaporators are usually designed considering rated load conditions. Residential heat pumps and residential air conditioners operate considerably longer at part load conditions than at rated load conditions. This study investigated the difference between a design considering the part load condition and a design considering the rated load condition in heat exchanger path design. The optimal number of paths for each load condition was selected considering the thermal resistance ratio. Results show that the heat transfer rates of a condenser with the optimal number of paths based on thermal resistance under 84%, 51%, and 33% load conditions were 18.29%, 27.58%, and 42.58% greater than the heat transfer rate of a condenser with the number of paths optimized under rated load conditions, respectively. Considering all load conditions, the optimal number of paths with the maximum average heat transfer rate was derived using the weighting factor of the system performance evaluation criteria. The results demonstrated that the optimal number of paths changed when a part load condition was considered in the heat exchanger design.

Ground testing of a 1% gravo-aeroelastically scaled additively-manufactured wind turbine blade with bio-inspired structural design

A gravo-aeroelastic scaling (GAS) method is developed to design wind turbine blades that represent centrifugal, aerodynamic, and gravitational loads of extreme-scale turbines. To match these elements, certain blade characteristics are given priority: non-dimensional 1st flap-wise frequency, non-dimensional flapping tip deflection, and tip-speed-ratio. Using the GAS method, a 1% sub-scale blade was designed to match the mass distributions and ground tested to match the non-dimensional flap-wise dynamics and deflections of Sandia National Lab’s 13.2-MW blade. To the authors’ knowledge, this is the first manufactured blade model to employ gravo-aeroelastic scaling using additive manufacturing and bio-inspiration. A series of scale models were designed, built, and ground-tested using weights consistent with scaled steady rated load conditions of an extreme-scale turbine. The models designed were evolved to increase gravo-elastic scaling performance by employing lightweight bio-inspirational morphology and carbon fiber reinforcements. The final version has non-dimensional gravo-elastic errors as follows: 3% in total mass, 15.6% in deflection from ground-based loads representing full-scale steady rated conditions, and 8.1% in the first flap-wise modal frequency (when normalized by the scaled rpm for rated conditions). This model demonstrates the GAS concept can be applied to manufacture sub-scale models as small as 1% of an extreme-scale rotor blade.

Soft-Switching Bidirectional Three-Level DC–DC Converter with Simple Auxiliary Circuit

This paper suggests a soft-switching bidirectional three-level DC–DC converter with a simple auxiliary circuit. The proposed converter uses auxiliary LC resonant circuits so that the power switches operate under a soft-switching condition. The resonant operation of the LC circuits makes power switches turn on at zero voltage, eliminating the turn-on switching power losses. The proposed converter improves the power efficiency, not using complex power switching circuits, but using simple LC resonant circuits. The operation of the proposed converter is described according to its operation modes. Experimental results for a 1.0 kW prototype are discussed to verify its performance. The proposed converter achieved the power efficiencies of 97.7% in the step-up mode and 97.8% in the step-down mode, respectively, for the rated load condition.

High-Reliable Temperature Prediction Considering Stray Load Loss for Large Induction Machine

Temperature prediction for electrical machines is a crucial concern in order to increase power density and ensure satisfactory life span. For high-reliable thermal analysis, this paper addresses a versatile methodology to apportion the stray load loss (SLL) of the induction machine. The 2-D transient finite-element analysis has been performed to investigate electromagnetic losses. The calculated losses under the rated-load condition are superimposed with the experimental SLL. The synthesized losses are imported to thermal-flow analysis using 3-D incompressible steady computational fluid dynamics. Electromagnetic losses, winding temperature, and air flow rate are measured with the test of a 1.8 MW medium voltage motor, validating the overall analysis and the allocation of SLL.

Electrical Performance Advancement in SiC Power Module Package Design With Kelvin Drain Connection and Low Parasitic Inductance

Silicon carbide (SiC) power modules are promising for high-power applications because of the high breakdown voltage, high operation temperature, low ON-resistance, and fast switching speed. However, the large parasitic inductance in existing package designs results in compromised performance, i.e., long blanking time in the desaturation protection scheme and large overvoltage spikes during the switching transient. Consequently, the benefits of SiC devices are often not fully utilized in practical applications. This paper deals with these two issues and aims at improving the electrical performance of the existing SiC module package. Specifically, a package design with Kelvin drain-to-source connection is first proposed to minimize the blanking time. More than 99% reduction of blanking time is achieved experimentally compared to the conventional package design. Second, a low parasitic inductance package with double-side cooling is proposed to allow the fast switching speed of SiC devices without sacrificing the thermal performance. A power loop inductance of 1.63 nH is realized from Q3D simulation. Verified by the experiment, more than 60% reduction of power loop inductance is achieved in comparison to a previously designed baseline module. At 0- $\Omega $ external gate resistance, the turn-off voltage spike is less than 9% of the dc-link voltage under the rated load condition.

Evaluation of Can eddy current losses and Can circulating current losses between the Can and end structures in double canned induction motors

The stator Can and rotor Can are unique structures in double canned induction motors, and Can losses include Can eddy current losses and Can circulating current losses between the Can and other end structures. However, the current research of Can losses is mainly focused on Can eddy current losses, and operation conditions are limited to the no-load condition, rated-load condition and start condition. Aiming at this problem, two kinds of Can losses are calculated and analysed in details. The influence factors are researched. Based on this, a reduction method of Can losses is proposed, and the efficiency curve is provided. Calculation results are compared with test values to validate the accuracy of the solving model. The reliable basis is provided for reducing Can losses in double canned induction motors.