Power Loss Model Research Articles

Power Losses of Oil-Bath-Lubricated Ball Bearings—A Focus on Churning Losses

This study investigates the power losses of rolling element bearings (REBs) lubricated using an oil bath. Experimental tests conducted on two different deep-groove ball bearings (DGBBs) provide valuable insights into the behaviour of DGBBs under different oil levels, generating essential data for developing accurate models of power losses. Observations of the oil bath dynamics reveal the formation of an oil ring at high oil levels, as observed for planetary gear trains, leading to modifications in the oil flow behaviour. The experiments demonstrate that oil bath lubrication generates power losses comparable to injection lubrication when the oil level is low. However, as the oil level increases, so do the power losses due to increased drag within the bearing. This study presents a comprehensive model for calculating drag losses. The proposed drag power loss model accounts for variations in oil level and significantly improves loss predictions. A comparison of existing models with the experimental results shows good agreement for both bearings, demonstrating the effectiveness of the developed model in accounting for oil bath height in loss calculations.

Comparison of Configurable Modular Two-Level and Three-Level Isolated Bidirectional DC–DC Converters for Super-Capacitor Charging in DC Shore Power Systems

Compared to the AC counterpart, the DC shore power system provides a significant advantage of efficient power supply from renewable sources to ships and onshore loads. Super-capacitors serve as key energy storage units in such a system to buffer the power fluctuations and collect the regenerative energy. However, the ultra-wide voltage range of super-capacitors imposes a significant challenge in the topology selection and efficiency optimization of the interfacing isolated bidirectional DC–DC converter. To tackle this challenge, this paper analyzes and compares two promising converter topologies, which are a configurable modular two-level dual-active bridge (CM-2L-DAB) and a three-level dual-active bridge (3L-DAB). To facilitate an ultra-wide voltage range, extended phase-shift (EPS) modulation in conjunction with the topology reconfiguration is analyzed for the CM-2L-DAB, while a hybrid modulation scheme is proposed for the 3L-DAB. A unified design approach is provided for both topologies, which also yields to the power loss modeling. On this basis, the CM-2L-DAB and 3L-DAB are thoroughly compared in terms of the modulation schemes, current stress, soft-switching operation, power conversion efficiency, material usage, closed-loop control scheme, and reliability. A prominent conclusion can be drawn that the CM-2L-DAB provides a higher efficiency than the 3L-DAB over the whole voltage range, but it relies on additional relays to reconfigure its topology which results in lower reliability and dynamic performance than the 3L-DAB.

Optimal‐droop voltage‐restorer for zonal dc distribution system with simultaneous consideration of dynamic current balance and power loss reduction

AbstractA dc voltage restorer (dc‐VR) with optimal droop control is developed to reduce the power loss and solve the dynamic current imbalance simultaneously of the zonal dc distribution system integrating multi‐parallel energy storage. Firstly, the power loss model composed of line loss and converter loss is built and it is proved to be a strictly convex function with respect to droop coefficients, which indicates the power loss can be mitigated by optimizing the current distribution. Thus, an image‐based droop optimization method is proposed to search for the optimal droop coefficients. Then, the economy of voltage compensation on power loss reduction is investigated and an ESS‐combined dc‐VR is designed, including an interleaved parallel architecture and a capacitor‐integrated electric spring (C‐ES). Unified virtual inertia is proposed for interleaved parallel bridge arms to make their dynamic performance consistent. And the newly introduced C‐ES can keep the bus voltage at the rated level to reduce the system cost. Therefore, the problem of dynamic currents imbalance is addressed from the points of converter structure (dc‐VR) and control system (unified inertia), and the power loss can be reduced by voltage recovery (C‐ES) and optimizing the current reallocation which is achieved by updating sharing coefficients from the image‐based droop optimization method. Finally, the simulation cases validate the effectiveness of the proposed optimal‐droop dc‐VR on dynamic current balance and power loss reduction, and hardware in the loop experiment results prove the consistent dynamic characteristics of the dc‐VR's arms.

On-line junction temperature identification of converter power devices

Abstract Traction converters often fail or age due to long operation hours, complex conditions, and frequent braking, mainly caused by overheating or temperature fluctuations. Monitoring the temperature at the junction of power device is crucial for system reliability. To achieve this, the electric-heat coupling models of IGBT are studied. Models for IGBT’s switching and conduction processes were created using its data sheet, yielding a power loss model linked to junction temperature. A Foster thermal network model for IGBT was then established, deriving the equation for temperature change when losses act as heat sources. Combining these models, an electric-heat coupling model was built on the SIMULINK platform, applied to predict and simulate junction temperature in a two-level inverter, generating a temperature-time image. Finally, an experimental test platform for a two-level SVPWM-modulated inverter was set up, using an infrared sensor to measure IGBT’s steady-state junction temperature. This was compared with simulation results to verify the model’s accuracy.

Advanced control of split source inverter through finite control-set model predictive control for improved system performance.

Distributed power generation systems may necessitate connecting multiple independent energy sources that employ various converter topologies. A recent development in this field is the emergence of impedance source converters, offering the ability to deliver buck-boost functionality within a single stage. The split-source inverter (SSI) has been introduced as a novel choice in between this family. Many control strategies have emerged for electrical power systems control. Among the recent emerging controllers, model predictive control strategies have become an effective technique for control systems. Model predictive controllers (MPCs) offer a number of features compared to the conventional and counterpart models such as enhanced system response and improved system transients with reduced steady-state error. This research suggests a finite control-set MPC for three-phase single-stage SSI supporting a standalone load for remote area applications. Considering the proposed FCS-MPC, the output load current tracks its reference magnitude with minimized error. In addition, the proposed FCS-MPC enhances the proposed SSI system performance with a settling time of 10 μs, and approximately without overshoot in the output current. The system has been validated using Opal-RT OP-4510 and the power loss model of the inverter has been explained. In the end two comparisons have been presented to clarify the main points in the topology structure and the control technique.

Performance evaluation of coupled-inductor DC-DC converter for wind energy conversion system

ABSTRACT This paper studies the performance of single-switch-coupled inductor-based quadratic DC-DC converter employed in the machine side converter of wind energy conversion system. The performance of the converter is evaluated in terms of voltage conversion ratio, voltage and current stress on the switch of the converter. The detailed circuit analysis, power loss analysis, modelling and integration issues have been elaborated in this work. The DC-link voltage regulation of wind energy conversion system is carried out using closed-loop control scheme including maximum power point tracking scheme and dual-loop control scheme. Simulation results and experimental results have been provided in this work.

Determination of Mechanical Power Loss of the Output Mechanisms with Serially Arranged Rollers in Cycloidal Gears While Taking into Account Manufacturing Tolerances

Despite their complex design, cycloidal gearboxes are characterized by high efficiency. Nevertheless, due to friction, some power is lost during gearbox operation. Basically, these losses occur in two structural nodes: the cycloid gearing and the output mechanism. Since the first of these nodes has been well discussed in the literature, the output mechanism will be discussed in this article. The design of the output mechanism has a significant impact on mechanical power losses. There are several mechanism design solutions. One of them is a mechanism with serially arranged rollers. Three solutions that are different in design but work identically will be discussed. Due to this affinity, a single, common mathematical model will be used to determine the value of losses. As will be shown, the value of losses is directly affected by the backlash, number, and diameter of the rollers used in the output mechanism and indirectly by the ratio and eccentricity of the cycloidal gearbox. Sample calculations were carried out using the developed model of mechanical power losses in the output mechanism. This made it possible to analyze the distribution of backlash created by manufacturing tolerances. It was also shown that the backlash has a significant effect on the number of rollers involved in torque transmission, as well as on the distribution of loads, contact pressures, and mechanical power losses.

High-Efficiency WPT Systems for Potable Electronics Based on DC-Bias-Voltage- Controlled Variable Capacitor

The power density of wireless power transfer (WPT) systems employed in portable electronics can be enhanced by increasing the operating frequency, but at the expense of lower efficiency due to increased switching and parasitic losses. This paper proposes a method, based on the DC-bias-voltage-controlled variable capacitor (VC) and variable frequency (VF) regulation, to improve the overall efficiency of the WPT system for portable electronics. The method uses VC on the primary side to detune the resonant tank and dynamically regulate the output power, while VF is employed to improve the system efficiency using a look-up table based on a power loss model. A DC bias voltage control module with self-supply ability is employed to control the equivalent capacitance of the VC. A control strategy is proposed to regulate both VC and VF. Experimental results of a 150W prototype are presented to demonstrate that constant output voltage can be maintained despite a wide load range, with an overall efficiency range of 82.1% (@25W) and 92.2% (@150W).

A general energy modeling network for serial industrial robots integrating physical mechanism priors

Industrial robots (IRs), as the core equipment of intelligent manufacturing, play increasingly important roles in various industrial scenarios such as assembly, welding, handling, and spraying, significantly improving production efficiency and product quality. The massive popularization and application of IRs have brought about a sharp increase in energy consumption (EC), and the modeling and optimization of EC is becoming imperative. In this paper, a general energy modeling network DM-PLM for serial IRs based on Dynamic Model (DM) and Power Loss Model (PLM) is proposed by integrating the prior knowledge of IR power composition and dynamic mechanism, enabling efficient and accurate modeling of dynamics, power, and EC under multi-load conditions. Considering the force transmission characteristics of serial robots, this paper proposes an improved bidirectional recurrent neural network (BiRNN) to model the joint dynamics. Additionally, a power loss model based on the ResNet convolutional neural network is employed. Experiments are carried out with a KUKA KR210 heavy-duty robot and a UR5 collaborative robot. The results show that the DM-PLM model incorporating the physical mechanism priors achieves 97 %, 98 %, and 99 % modeling accuracy in joint torques, total power, and EC for both robots under multi-load conditions. In addition, the proposed DM-PLM model is applied to the EC optimization of KUKA KR210 through trajectory planning, which achieves over 30 % EC reduction with the genetic algorithm, providing an effective approach to improving the energy efficiency of serial IRs.

Power Loss Modelling and Performance Comparison of Three-Level GaN-Based Inverters Used for Electric Traction

The main aim of this work is to present a step-by-step procedure to model and analyze the power loss distribution of three-level Gallium Nitride (GaN) inverters. It has been applied to three distinct three-phase three-level voltage source inverters utilized in electric traction drives: Active Neutral Point Clamped, Neutral Point Clamped and T-Type Neutral Point Clamped. The proposed analytical power loss modelling, combined with an equivalent representation of the electrical machine proved to be a viable solution to achieve a time-saving and low computational burden simulation platform, leading to satisfying accurate results. This has been confirmed by comparing the results carried out from the simulations of a 110 kW permanent magnet synchronous motor drive and those determined by considering a simplified circuital representation based on the proposed analytical power loss modelling.

Power loss model of electromagnetic waves propagation in cell solutions by GHz electrical impedance spectroscopy

The propagation of GHz electromagnetic (EM) waves across cells in cell solutions has been analytically modeled and numerically calculated in order to elucidate the power loss in the boundary between dispersed medium and cell by establishing a theoretical model. Living and dead yeast cells are chosen as objects because of the simple cell structure and ease of observation under optical microscope. Through the model, the average power density of the incident wave S avi , reflected wave S avr , transmitted wave S avt , and ratio of the power loss ψ are calculated and compared to analyze the power loss of EM waves inside living and dead yeast cells by considering the impacts of frequency of EM wave, cell viability, concentration, and component structures of the cell. Results demonstrate decreased S avi, S avr , and S avt with rising frequency, especially noticeable below 100 MHz due to enhanced absorption from cell components. EM waves in living yeast cell solutions exhibit faster attenuation and stronger reflection compared to dead yeast cells, attributed to intact organelles and membranes intensifying absorption and scattering. The increasing cells concentration further attenuates EM waves. This work elucidates propagation and power loss of EM waves in cell solutions and provides an effective computational approach to optimize EM wave based biomedical applications.

Considerations on the Development of High-Power Density Inverters for Highly Integrated Motor Drives

In transportation electrification, power modules are considered the best choice for power switches to build a high-power inverter. Recently, several studies have presented prototypes that use parallel discrete MOSFETs and show similar overall output capabilities. This paper aims to compare the maximum output power and losses of inverters with different types (surface-mounted, through-hole-mounted and power modules) of commercially available switching devices, and, therefore, discuss the theoretical boundaries of each technology. The numerical analysis relies on detailed power loss and thermal models, with adjustments made for gate current and realistic parameters of the cooling system. The analysis includes two case studies with different targets, including minimum dimensional characteristics and maximum output power. The results demonstrate that discrete MOSFETs can provide improved capabilities in contrast to power modules under certain conditions.

Power Loss Modeling and Impact of Current Measurement on the Switching Characterization in Enhancement-mode GaN Transistors

Power Loss Modeling and Impact of Current Measurement on the Switching Characterization in Enhancement-mode GaN Transistors

An instant loss analysis model for complex magnetic core materials

This paper tries to deduce the time domain model of magnetic power loss without integral term from the basic magnetic induction, eddy loss, and supposed hysteresis loss equations. Based on the results of the50~5000Hz frequency domain and magnetic flux density of 0.1~1.8T, the overall average error rate is lower than 6%. It applies to both periodic and non-periodic magnetic field conditions. Based on the new instant loss equation in the changing magnetic field, the power loss of magnetic materials includes the induced eddy current loss. It is related to the instantaneous variation of the reciprocal of the magnetic permeability. It is found that the hysteresis loss is dependent on the saturation of magnetic field intensity.

Lubrication characteristics of valve plate pair of balanced large flow pump based on elastic deformation

In this paper, the balanced large flow pump is taken as the research object. Considering the elastic deformation of the surface of the valve plate pair, the oil film dynamic model and the power loss model of valve plate pair are established, and the influence of different working conditions on the lubrication characteristics of valve plate pair is analyzed. The results show that the oil film parameters and performance parameters of valve plate pair change periodically. The power loss of valve plate pair is mainly viscous friction power loss, and the leakage power loss is small; considering the elastic deformation, the viscous friction power loss is reduced by 2.73 %–3.61 %, and the leakage power loss is increased by 21.8 %–25.3 %. The increase of working pressure and rotating speed will increase friction and leakage power loss. The increase of internal and external swash plate inclination will reduce the friction power loss and increase the leakage power loss. Compared with the traditional single-row axial piston pump, the viscous friction torque of the balance pump decreases and the leakage increases, but the total power loss decreases, which makes the balance pump more efficient than the traditional pump.

Hybrid Data-Mechanism Modeling for Power Loss of a Boost Converter

Parameter design is the premise to ensure the optimal performance of power electronic converters, which depends on the accuracy of the established model. However, there is still many issues for improvements in modeling methods for the parameters design of power electronic converters. Due to the lack of key mechanism and the uncertainty of parameters, the existing modeling method shows poor accuracy or efficiency. In order to simplify the process and improve the accuracy of the existing modeling method, this paper proposes a hybrid data-mechanism modeling (HDMM) method for power loss of a typical power electronic converter, Boost converter, which is with UC3842 control chip. Based on the main loss from inductor, switch tube, diode and sampling resistance, the mechanism power loss modeling of Boost converter is built. Besides, the artificial neural network (ANN) is used to learn from the sampled data and train the data-driven model. To improve the accuracy of the mechanism model, the HDMM for power loss of Boost converter is established by modification of data-driven model with limited data. Through the proposed HDMM method, the mechanism modeling method and data-driven method are well combined and the HDMM has the advantage of high accuracy and strong generalization. In the end of this paper, feasibility and accuracy of the proposed HDMM method have been verified by hardware experiments.

Dynamic torque coordination control of dual-motor all-wheel drive axles to suppress the longitudinal jerk of the vehicle

The switching of multiple working modes between power sources or axles through an economic torque distribution strategy can cause longitudinal jerk problems in electric vehicles equipped with multiple power sources and multi-axle drive systems. To address this issue, an online real-time dynamic torque distribution strategy was proposed. This strategy can suppress the longitudinal jerks in real-time and minimize the total power loss of the vehicle. In this study, a vehicle dynamics model, which considers a nonlinear system, is developed to reflect the transient process of the torque dynamic response of a vehicle transmission system. The main factors influencing the longitudinal jerk of the vehicle were analyzed. To minimize the total power loss of the vehicle, a dynamic power loss model of the electric drive system is established, and the model accuracy is experimentally verified. Through optimal control theory, this study proposes an online real-time dynamic torque distribution strategy that achieves the lowest total power loss of a vehicle while suppressing the longitudinal jerk. Under WLTC conditions, the longitudinal jerk is reduced by 79.46 % during mode switching, resulting in improved driving comfort, and the effectiveness of this strategy is verified via the experimental bench of the dual-motor four-wheel-drive electric drive system.

Optimal gear ratio selection of linear primary permanent magnet vernier machines for wave energy applications

AbstractLinear permanent magnet vernier generators offer a high capability of force density, making them appealing configurations for wave energy harvesting systems. In absolute terms, the performance of these machines is significantly influenced by the selection of slot/pole combinations based on the magnetic gearing effect. For the first time, this paper aims to investigate the impact of different gear ratios on a wide array of linear primary permanent magnet vernier machines (LPPMVMs) with different slot/pole combinations based on fair criteria to offer a more comprehensive understanding of gear ratio selection. To find the optimal number of slots and poles, the response surface methodology is adopted to obtain a robust design and make a fair comparison among LPPMVMs with optimum design characteristics using a cost‐effective approach for the fast and reliable optimisation process. The higher gear ratios result in higher thrust force capability. This will help establishing a new route toward faster develpment of advanced LPPMVMs. The power loss models of LPPMVMs are studied to predict their steady‐state and transient thermal behaviours, verifying their stability and safety, while a simple external forced convection method can be utilised. To verify the model, finite element analysis is exploited to confirm the electromagnetic and thermal analysis results and provide a more exhaustive investigation.

Research on internal flow field analysis and power loss modeling of the expansion seal ring

Expansion seal rings are widely used in automobile transmission systems, and their sealing performance plays a vital role in the pressure stability and transmission efficiency of the transmission system. However, investigations into revealing the internal flow mechanism of the expansion seal ring and predicting the power loss of the expansion seal ring are still insufficient. In this study, a two-way fluid–structure interaction model consisting of the shaft, oil sleeve, and expansion seal ring was established. The flow and structural physical fields under a series of operating conditions were simulated, and the effects of oil temperature, rotational speed, and seal pressure differential on leakage rate, deformation, power loss, and contact pressure were analyzed. Further, a power loss prediction model was developed by multiple linear regression method. The results demonstrate that in the internal flow field, the oil flow into and out of the groove is characterized by backward step flow and jet flow, respectively. In the structural field, the maximum deformation and the maximum contact pressure of the main sealing surface appear at the notch of the expansion seal ring, and the seal pressure differential has the most significant influence on it. The relative error between the predicted value of the developed model and experimental values is within 9%, which meets the industrial requirements. This work facilitates scholars to understand the internal flow mechanism and deformation process of expanding seal rings and provides a method to predict sealing ring power loss.

Testing and modelling of a 2.5 MW wind turbine gearbox: Influence of lubricant formulation

AbstractThis study aimed to evaluate the efficiency of different ISO VG 320 oil formulations used in a 2.5 MW wind turbine gearbox. Two commercially available lubricants, a mineral oil and a polyalphaolefin (PAO) lubricant, were tested under realistic operating conditions using a customized test rig.Measurements showed that the overall efficiency of the mineral lubricant was higher than that of the PAO lubricant, but the difference was only 0.1% in degree of efficiency. Detailed oil analysis revealed that the mineral lubricant generated more wear particles.A power loss model was also implemented to predict the efficiency of the gearbox, and the results of the model were found to be in agreement with the experimental results. The study concluded that the mineral oil presented higher efficiency than the PAO oil due to its lower viscosity within the narrow operating temperature range imposed on the gearbox. Nevertheless, it is important to note that the observed differences in efficiency may be attributed, in part, to measurement uncertainties and the fact that the mineral lubricant has 10% lower viscosity at the operating temperature compared to the PAO lubricant.