Theoretically, the layout of fractional pitch permanent magnet motors should ensure the cancellation of most cogging torque harmonics. In reality, manufacturing errors lead to incomplete cancellation ...and higher than expected cogging torque. One potential manufacturing error is the variation in angle between neighboring magnets. This paper uses the superposition technique to analytically determine the expected magnitude of each cogging torque harmonic based on a Gaussian distribution of angular magnet placement variation. A simple expression is presented for the expected value of each harmonic's magnitude based upon the harmonic number, the number of magnets, and the standard deviation of the Gaussian placement distribution. The derived expression is validated using Monte Carlo simulations and experimental implementation.
A computationally efficient method is presented to investigate additional cogging torque harmonics resulting from misalignment of the rotor and stator caused by assembly and manufacturing tolerances ...in an axial flux fractional pitch permanent magnet synchronous machine (PMSM). The superposition method creates a complete cogging torque profile by using a library of pole transitions over a single stator slot. The method extends previously published work, and is used to predict the effect of eccentricity misalignment in combination with pole and slot placement inaccuracies on cogging torque. Experimental data are presented supporting the superposition data indicating that static and dynamic eccentricity produce first- and second-order sidebands about the rotor and stator affected harmonics, respectively. There is good agreement between the hybrid superposition method, FEA, and measured experimental data.
In the last decade, maybe longer, the oil, gas and chemical (OGC) industry has seen a decline in the electric power engineering ranks and knowledge base. With the advent of the pandemic and the great ...resignation that followed, the industry has seen an acceleration of this knowledge drain. As experienced workers retire, knowledge around engineering and design of electrical systems and the application of various products is leaving with them, and hence engineers are being tasked with doing more sooner. Many universities have shifted the focus of their curriculums to cater to the field of high tech, leaving only a handful of institutions with strong programs in electric power engineering and subfields such as electric machines, power electronics, and power systems. Addressing skill gaps has become a point of discussion from break rooms to board rooms. One clear example is the sizing of Medium and Low Voltage power cables, which are critical to the supply of electric power in all industries. Selecting and sizing cables can have a material impact on the overall reliability, safety, and CAPEX cost of a project. This article discusses a cable sizing flowchart tool as a means to mitigate the knowledge drain caused by engineers retiring and resigning in the OGC industry. The tool brings relevant knowledge that resides in the National Electrical Code (NEC) around cables and selecting the right size of cable using the Low Voltage Cable Sizing Flowchart in Appendix <xref ref-type="app" rid="app1">A , based on 2023 NEC. The goal of the paper is to provide a handy reference cable sizing guide for the early career professional who is asked to make cable selections and to serve as a springboard for further reference depending on the specific application that the engineer might be tasked with.
This paper proposes a systematic multi-step design procedure for highly efficient printed circuit board (PCB) stator coreless axial flux permanent magnet (AFPM) machines with minimal eddy and ...circulating current losses. The process begins with initial sizing, providing specific coefficients based on experience with multiple design projects. It continues with the optimization of the machine envelope design using an evolutionary algorithm and computationally efficient 3D finite element analysis (FEA) models. The subsequent step focuses on the detailed design of a PCB stator, aiming to minimize eddy and circulating current losses. Several open circuit loss mitigation techniques are proposed based on analytical equations and 3D FEA, while considering PCB manufacturing limitations and standards. The effectiveness of this design procedure is showcased through the design of an integral horsepower PCB stator coreless AFPM machine for HVAC applications, which was prototyped and tested. The experimental results indicated significantly reduced eddy current losses and virtually zero circulating currents, achieving 96% efficiency at a speed of 2,100rpm and an output torque of 19Nm. This outcome validates the efficacy of the proposed approach.
Removing some sections of the stator yoke in a permanent-magnet brushless machine can be beneficial for reducing punching waste and simplifying motor manufacture. However, in some cases, restricting ...the possible flux paths, in this way, will have a detrimental impact on the torque and air-gap harmonics. This paper discusses the potential implications of modular stator core arrangements and presents the air-gap flux density harmonics and winding factors for potential slot/pole combinations. Finite-element analysis (FEA) simulations are presented to support the analytical calculations. The analysis indicates that the performance reduction from using a modular stator is minimal when the number of slots and poles are similar but drops off substantially when this is not the case. A modular core stator will increase the MMF subharmonics due to the magnet field but can reduce the subharmonics due to the armature if a single-layer winding is used. The effect of slotting is very similar for a modular and conventional core machine, and FEA results match previously published analytical analyses.
Bearing voltages and associated bearing currents in electric machines driven by pulsewidth modulation converters with high switching frequencies and high <inline-formula><tex-math ...notation="LaTeX">dv/dt</tex-math></inline-formula> can cause premature bearing failures. This article proposes a new modeling approach for the prediction of steady-state and transient bearing voltages based on two-dimensional (2-D) electromagnetic finite element analysis with coupled external circuits using measured bearing capacitance values. The distributed-element external circuit was employed mainly to take into account the influence of wire distribution and frequency dependency, which are typically neglected by traditional equivalent circuits. The developed model was then used to simulate bearing voltages for various scenarios and evaluate the effectiveness of several easy-to-implement bearing voltage reduction methods from the perspective of machine design and manufacturing, such as using the insulated shaft and/or bearings, introducing additional insulation in the rotor, and changing the material of machine components. Experimental measurements are also provided to facilitate the analysis and validate the proposed approach.
In the process of designing and manufacturing an electrical machine, a systematic study of dimensional and material tolerances is of the utmost importance. This paper proposes a systematic method by ...which the effect of design specification variations on permanent magnet (PM) synchronous machine performance may be identified and quantified. The method combines design of experiments techniques, open-circuit and short-circuit physical measurements, and virtual test simulations conducted based on the recently approved IEEE Std 1812 testing guide. Three case studies, two provided by a spoke-type PM radial field machine configuration, in two designs with different electromagnetic loading, and an axial flux PM machine are discussed. It is shown that based on the output performance, out of specification tolerances for magnet remanence, steel grade, as well as dimensional variables, and stator to rotor eccentricity, may be identified under certain conditions. It is also exemplified that the ratings, magnetic loading, and configuration of the machine play critical roles and should be thoroughly considered as part of the studies.
This article argues that low latency, high bandwidth, device proliferation, sustainable digital infrastructure, and data privacy and sovereignty continue to motivate the need for edge computing ...research even though its initial concepts were formulated more than a decade ago.
Permanent-magnet synchronous machines are a high-efficiency motion solution. As the efficiency bar is raised, it is no longer adequate to consider only the dominant core, dc conduction, and friction ...losses. The challenge for motor developers experiencing additional losses is determining which of the previously neglected losses is significant for their motor. This research presents a best-fit least-squares approach to loss separation that can be applied to experimental data to highlight the source of additional losses. This is a powerful tool for practical motor designers looking to meet challenging specifications. The proposed technique has been applied to the experimental data from three different prototype motors. Although a simple core model of core loss is used, in each case the losses were classified with a residual of less than 2%. Each loss type (defined by proportionality to speed and current) showed good agreement with the corresponding loss type calculated from finite-element analysis (FEA).
Accurate Torque Ripple Measurement for PMSM Heins, G.; Thiele, M.; Brown, T.
IEEE transactions on instrumentation and measurement,
2011-Dec., 2011-12-00, 20111201, Volume:
60, Issue:
12
Journal Article
Peer reviewed
Torque ripple in permanent-magnet synchronous motors is generally undesirable. Significant work has been done to minimize this torque, either by modifying the mechanical motor design or by careful ...controller design. Surprisingly, however, little work has been published on the accuracy of torque ripple measurement. A successful measurement requires a mechanical design with readily modeled dynamics, sensors with suitable bandwidth and resolution, a method of applying a smooth load to the motor, and a method for calibrating the measurement. This paper presents a thorough approach to the accurate measurement of torque ripple. The proposed system has been validated by finite-element modeling, analytical calculations, and experimental analysis.
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