High Power Density Machines Research Articles

An Overview of Electric Machine Trends in Modern Electric Vehicles

Electric machines are critical components of the drivetrains of electric vehicles. Over the past few years the majority of traction drive systems have converged toward containing some form of a permanent magnet machine. There is increasing tendency toward the improvement of power density and efficiency of traction machines, thereby giving rise to innovative designs and improvements of basic machine topologies and the emergence of new classes of machines. This paper provides an overview of present trends toward high specific power density machines for traction drive systems. The focus will be on current technology and the trends that are likely to be pursued in the near future to achieve the high specific power goals set for the industry. The paper discusses machines that are applied in both hybrid and battery electric drivetrains without distinction and does not discuss the associated power electronic inverters. Future electric machine trends that are likely to occur are also projected.

Experimental analysis of contact fatigue damage using fractal methodologies

Gears are used in high power density (power throughput/weight) machines for continuous power transmission. The efficiency and reliability of gears significantly depend on tribological performance. Micropitting is a type of rolling contact fatigue damage mechanism that occurs at the asperity scale in lubricated contacts and highly prevalent in gears. A detailed surface characterization study is essential to get an insight into the incident of micropitting. In this work, factors affecting resistance to micropitting are investigated by performing series of twin disk experiments. The effect of disc geometry and slide-to-roll ratio on resistance to micropitting is discussed in detail. It is observed that micro pits coalesces occur when components run for very large number of fatigue cycles. A positive correlation is found between autocorrelation length and surface damage. Rose plot and area-scale fractal analysis is employed on damaged surfaces, and it is concluded that there exists a certain scale, below which fractal theory is applicable.

Graphene: future of high power density electrical machines for electric vehicle applications

The key challenges faced by many of the industries in the present scenario is to develop a high power density electrical machine. The advancements in material technology help the industries to enhance the power density as well as the efficiency of an electrical machine to a greater extent. Conductors play a major role in improving the machine's performance. In this paper, the role of conducting materials in high power density electrical machines are discussed. Graphene is an advanced nanomaterial that exhibits excellent conductivities with low mass density. Using graphene coated windings, the weight and volume of the machine can be reduced significantly. In order to understand the prominent features of the nanomaterial based conductors, a case study has been carried out in different electric vehicles such as Toyota Prius (2017), Nissan LEAF and BMW i3. Moreover, a major constraint in high power density machine is the temperature rise, which is discussed at the end.

Experimental investigation on evolution of surface damage and topography parameters during rolling contact fatigue tests

AbstractNowadays, micropitting is perceived as one of the prevalent wear mechanisms, which is responsible for the breakdown of high power density (power throughput/weight) machines. The current work demonstrates the evolution of surface damage and surface topography parameters during micropitting tests. The test surfaces are examined at different load stages utilizing 3D optical profiler, optical microscope, and scanning electron microscope. The effect of slide‐to‐roll ratio (SRR) on surface damage and topography parameters is also presented. It is observed that the severity of micropitting increases with an increase in the number of cycles. It is concluded that surface bearing index (Sbi), kurtosis (Sku), maximum valley height (Sv), and autocorrelation length (Sal) are positively correlated with surface damage, whereas mean summit curvature (Ssc) and skewness (Ssk) are negatively correlated with surface damage. Surface texture ratio (Str) and power spectral density (PSD) of test surfaces are used for analysing surface texture, and it is found that deterioration in surface texture occurs after 6 million cycles. It is also concluded that geometrical isotropy increases with an increase in SRR.

Design and Losses Analysis of a High Power Density Machine for Flooded Pump Applications

This paper describes the design process of a 10 kW 19 000 r/min high power density surface mounted permanent magnet synchronous machine for a directly coupled pump application. In order to meet the required specifications, a compact machine with cooling channels inside the slots and flooded airgap has been designed through finite element (FE) optimization. For high power density, high-speed machines, an accurate evaluation of the power losses, and the electromechanical performance is always extremely challenging. In this case, the completely flooded application adds to the general complexity. Therefore, this paper deals with a detailed losses analysis (copper, core, eddy current, and mechanical losses) considering several operating conditions. The experimental measurements of ac copper losses, as well as the material properties (BH curve and specific core losses) including the manufacturing process effect on the stator core, are presented. Accurate 3-D FE models and computational fluid dynamics analysis have been used to determine the eddy current losses in the rotor and windage losses, respectively. Based on these detailed analysis, the no-load and full-load performance are evaluated. The experimental results on the manufactured prototype are finally presented to validate the machine design.

Magnetic characterization of the nickel layer protecting the copper wires in harsh applications

Abstract High Temperature (HT°) motor coils open new perspectives for extending the applications of electrical motors or generators to very harsh environments or for designing very high power density machines working with high internal temperature gradients. Over a temperature of 300°C, the classic enameled wire cannot work permanently, the turn-to-turn insulation must be inorganic and made with high temperature textiles or vitro-ceramic compounds. For both cases, a diffusion barrier must protect the copper wire against oxidation. The usual solution consists of adding a nickel layer that yields an excellent chemical protection. Unfortunately, the nickel has ferromagnetic properties that change a lot the skin effect in the HT wire at high frequencies. For many applications such as aeronautics, electrical machines are always associated with PWM inverters for their control. The windings must resist to high voltage short spikes caused by the fast fronted pulses imposed by the feeding inverter. The nickel protection layer of the HT° inorganic wire has a large influence on the high frequency behavior of coils and, consequently, on the magnitude of the voltage spikes. A good knowledge of the non-linear magnetic characteristics of this nickel layer is helpful for designing reliable HT inorganic coils. The paper presents a method able to characterize non-linear electromagnetic properties of this nickel layer up to 500°C.

Compression Ignition Engines – Revolutionary Technology That has Civilized Frontiers all Over the Globe from the Industrial Revolution into the Twenty-First Century

The history, present and future of the compression ignition engine is a fascinating story that spans over 100 years, from the time of Rudolf Diesel to the highly regulated and computerized engines of the 21st Century. The development of these engines provided inexpensive, reliable and high power density machines to allow transportation, construction and farming to be more productive with less human effort than in any previous period of human history. The concept that fuels could be consumed efficiently and effectively with only the ignition of pressurized and heated air was a significant departure from the previous coal-burning architecture of the 1800s. Today, the compression ignition engine is undergoing yet another revolution. The equipment that provides transport, builds roads and infrastructure, and harvests the food we eat needs to meet more stringent requirements than ever before. How successfully 21st Century engineers are able to make compression ignition engine technology meet these demands will be of major influence in assisting developing nations (with over 50% of the world’s population) achieve the economic and environmental goals they seek.

Research on the Torque and Back EMF Performance of a High Speed PMSM Used for Flywheel Energy Storage

Due to advantages such as high energy density, high power density, rapid charge and discharge, high cyclic-life, and environmentally friendly, flywheel energy storage systems (FESs) are widely used in various fields. However, the performance of FES systems depends on the performance of a high speed machine, therefore, the design and optimization of a high efficiency and high power density machine are very crucial to improve the performance of the whole FES system. In this paper, a high speed permanent-magnet synchronous machine (PMSM) is researched. Considering the requirement of low torque ripple in low speed and loss caused by back electromotive force (EMF) harmonics, the electromagnetic performance is improved from points of view of slot/pole matching, magnetic-pole embrace with the finite element method (FEM). Furthermore, the magnetic-pole eccentricity, the slot opening, the thickness of PM and air-gap length are also optimized with Taguchi method. The electromagnetic performance, such as torque ripple, cogging torque, average torque and back EMF wave are much improved after optimization. Finally, experiments are carried out to verify the calculated results.

A comparison between axial and radial flux PM motor by optimum design method from the required output NT characteristics

Purpose – To design a high power density machine, an automatic design method is proposed. Hopefully, automatic design method uses only the requirements (torque and speed) and the information about sources (voltage and current).Design/methodology/approach – To calculate the volume, a necessary flux density and an inductance are calculated by the permeance method. All mechanical parameters, stator diameter, teeth width, turn number and so on, realize the necessary flux density and an inductance, and these parameters are expressed as a function of a rotor diameter. By using both conditions of current density and copper loss, a rotor diameter which realizes the minimum volume can be obtained.Findings – As a result of an optimum design, 50 kW SPMSM is realized only into 2[L] spaces, which copper loss is only 500[W], 1 percent of the maximum output. Moreover, 50 kW axial flux type machine is realized only into 1.3[L] spaces. Accurate comparison is possible by only optimum designs because these have the solution...

Optimization of power density for axial-flux machine through generalized sizing equations

With the evolution of various high power-density machines, it becomes important to optimize the power potential of machines of vastly different topologies with a variety of waveforms of back emf and current. The approach of this paper is based on the general-purpose sizing equations which permit the optimization method of machine power density to be applied to the axial-flux toroidal permanent-magnet (AFTPM) machine, and, furthermore, the power-production capabilities of the AFTPM machine and the well-known squirrel-cage induction machine are compared.