Motor Core Losses Research Articles

Enhancing Performance of Permanent Magnet Motor Drives through Equivalent Circuit Models Considering Core Loss

Permanent magnet motors (PMMs) have emerged as key components in numerous industrial applications due to their high efficiency, compact size, and robust performance characteristics. However, to attain optimal performance in PMM drives, accurately predicting and mitigating core losses is paramount. This paper aims to provide a comprehensive review of advancements and methodologies for enhancing the performance of PMM drives by integrating equivalent circuit models (ECMs) that account for core losses. Firstly, the significance of core losses in motor drives is underscored, alongside a survey of research endeavors dedicated to core loss reduction. Notably, emphasis is placed on mathematical models offering both swift computation and reasonable accuracy. Subsequently, the paper delves into the development of ECMs, focusing on approaches adept at capturing core loss effects across diverse operating conditions. Moreover, this paper explores the utilization of these improved ECMs in the design and control of PMMs to achieve enhanced performance. By integrating core loss considerations into design and control strategies, PMM drives can optimize efficiency, torque production, and overall system performance. In summary, this paper may consolidate the current state-of-the-art techniques for enhancing PMM performance through the integration of core-loss-aware ECMs. It highlights key research directions and opportunities for further advancements in this critical area, aiming to foster the development of more efficient and reliable PMM-based systems for a wide range of industrial applications.

Switched reluctance motor core loss estimation with a new method based on static finite elements

Switched reluctance motor core loss estimation with a new method based on static finite elements

Magnetic properties of an Fe-based amorphous soft magnetic composite prepared via in-situ steam oxidation

Reducing the core losses of motors and transformers is an important way to address the global environment and energy resource problems. Soft magnetic composites (SMCs) comprising of electrically insulated ferromagnetic powder has shown vast potential for applications at low to high applied frequencies. In this work, in-situ steam oxidation was used to coat the surface of amorphous Fe75.5Si4B6P8C6Mo0.5 powder with an insulating layer. The thickness and composition of the Fe-oxide layer were controlled by tuning the in-situ steam oxidation time, and more cracks and Fe2+ were formed on the powder surface with the extension of oxidation time. The magnetic Fe-oxide layer of amorphous powder not only plays an insulating role to reduce the Pe, but also affects the magnetic coupling of particles that leads to the change of Ph. And the amorphous SMCs with 10 h in-situ steam oxidation treatment exhibits good comprehensive soft magnetic properties, i.e., the magnetic loss (Pcv), effective permeability (μe) and DC bias are 61.44 W/kg (50 mT, 100 kHz), 30.4 (to 10 MHz) and 71.5% (100 Oe), respectively.

Improved calculation of core losses of high-speed motors with two different permanent magnets considering higher order current harmonics

In high-speed permanent magnet synchronous motor drives, time harmonics in the current occur owing to the carrier frequency of the inverter, which affects the core losses among the electromagnetic losses. According to Steinmetz’s equation, the core loss depends on the frequency and magnetic flux density, with each term influenced by harmonic currents. Therefore, to accurately predict core loss, it is necessary to consider harmonic currents. This study presents the effects of differences in the resistance, inductance, switching frequency, and harmonic current on the core loss for two models with different PMs at the same output power. Core losses are significantly affected by harmonic current content and magnetic field behavior, making the analysis of harmonic components and magnetic field behavior essential. To achieve this, the stator core was divided into segments to examine the magnetic field behavior owing to harmonic currents in each region, thus facilitating a comprehensive analysis of the core losses. When the results were compared with the experimental data, it was observed that the analysis of harmonic currents significantly improved the accuracy compared to the analysis based solely on sinusoidal currents; in particular, the error rate reduced from 37.8% to 4.1%. Furthermore, it was confirmed that ferrite PMs resulted in smaller core losses owing to harmonic currents than rare-earth PMs. This finding suggests that ferrite PMs are a suitable alternative to high-speed permanent-magnet synchronous motors.

Experimental study of mutual effects of high carrier frequency, dead-time and control sample time on IPMSM core loss under SiC inverter excitation

This paper experimentally analyzes the core loss characteristics of an interior permanent magnet synchronous motor (IPMSM) excited by a SiC inverter with the sinusoidal pulse-width modulation (PWM) and high modulation index of 1.1 considering the mutual effects of the high carrier frequencies of up to 200 kHz, different dead-times of 250 and 1000 ns, control sample times of 100–1000 μs, and stator core temperature. The experimental IPMSM drive system is operated in load condition with a torque of 1.05 Nm and rotational velocity of 1500 rpm. Furthermore, the ringing phenomenon and rise time in the motor voltage are measured and analyzed using a high-resolution oscilloscope that has a superior sampling rate of up to 5 giga-samples per second (GS/s), which helps to thoroughly examine the impact of the SiC inverter excitation on the motor core loss. The relations of the total harmonic distortion (THD) of the measured motor voltage and current and the distortions in the magnetic flux density through the stator core to the IPMSM core loss properties are also evaluated. Lastly, explanations and insights based on physics of the obtained results are presented.

Reduction of Motor Drive System Loss by 5th Harmonic Superimposition PWM Control

Herein, the loss reduction of a motor drive system is experimentally studied by means of the 5th harmonic superimposition in the reference signal of a sinusoidal PWM inverter from the perspective of nonlinear magnetic characteristics. The measured data of the motor drive system loss exhibits a reduction of 1.5% in the condition when the superimposition rate is -0.15. More specifically, the motor core, copper and inverter losses are reduced. The results confirm the feasibility and efficacy of the proposed method. According to the fundamental research of a ring test with the same electrical steel as the motor, the magnetic characteristics of the B-H curve changes in the case of the 5th harmonic superimposition, which decreases the fundamental component of the current. Accordingly, the loss is considered to be reduced due to the decline in the fundamental current component and carrier frequency components.

Synthesizing the Optimal Control of an Induction Motor-Based Traction Electric Drive with Taking into Account Magnetic Saturation and Core Losses

Traction electric drives based on an induction motor often employ vector control with orienting along the rotor flux vector, with which it becomes possible to achieve high performance indicators of the motor and drive as a whole in both static and dynamic operation modes. However, to achieve high energy efficiency of the drive, the use of optimal control strategies becomes of issue. This implies the need to set up, given a specified electromagnetic torque, the stator current flux-forming and torque-forming components according to a certain law to achieve the motor operation optimized with respect to the selected criterion. In the context of a traction electric drive, such criteria are stator current to be maximized or power losses to be minimized. In doing so, it is important to take into account the motor magnetic system saturation and core losses, which have a significant impact on the synthesis of optimal control strategies. The article gives the equations of electromagnetic processes in a cage induction motor with field-oriented control and with taking into account the above-mentioned specific features. A procedure for synthesizing optimal control strategies while minimizing power losses and stator current is also given. Differences in approaches to the synthesis of optimal strategies with and without taking the magnetic system saturation into account are shown.

Design of Stator Winding Turn Number of Tap-Change PMSM for EVs According to Driving Cycles

Driving cycles are commonly used to evaluate the fuel efficiency and mileage of internal combustion engine vehicles and electric vehicles (EVs). To improve the mileage of EVs, efficient propulsion motors and inverters must be employed, particularly at frequently used speed and torque points of driving cycles. In this study, the number of the stator winding turns of a tap-change permanent magnet synchronous motor (PMSM) used for EV propulsion was investigated to increase the motor and inverter energy efficiencies under an urban dynamometer driving schedule (UDDS), a highway fuel economy test (HWFET), and combined UDDS/HWFET driving cycles. The motor core loss due to the carrier harmonics, copper loss, and inverter loss were analyzed for various winding turn number combinations, and the most efficient combination was selected. Based on the analysis results, the tap-change motor winding turns that exhibited the least loss were rewound on a PMSM of a mass-produced EV. The demand energy of the proposed tap-change PMSM and that of a mass-produced PMSM in the UDDS, HWFET, and combined UDDS/HWFET driving cycles were compared through experimentation. The proposed PMSM exhibited energy improvements of 1.50%, 1.84%, and 1.65%, respectively.

Corrigendum: Assessment of motor core loss, copper loss and magnetic flux density with PAM inverter under dissimilar excitation angles

Corrigendum: Assessment of motor core loss, copper loss and magnetic flux density with PAM inverter under dissimilar excitation angles

A thermographic camera method for measuring the core loss distribution

Motor core losses are usually evaluated as the total loss minus known losses, including copper and mechanical losses. However, it is difficult to identify the main cause of core losses based on this evaluation method. In our previous study, we proposed a method for directly evaluating core loss distribution based on heat measurements using a thermographic camera. In this paper, we examine the reliability of thermal measurements using a device that can simultaneously measure core loss both by the general magnetic method and by the thermal measurement method. In the comparison method, the magnetic loss and thermal measurements are conducted simultaneously using an open magnetic path single sheet tester that permits simultaneous direct imaging of a sample with a thermographic camera, and the core loss values are compared and examined. We demonstrate a good agreement between the thermal and magnetic measurement below 10% difference for flux densities higher than 1T.

Assessment of motor core loss, copper loss and magnetic flux density with PAM inverter under dissimilar excitation angles

This study is the first research to present a detailed assessment of core loss, copper loss and magnetic flux density of the interior permanent magnet synchronous motor (IPMSM) with pulse-amplitude modulation (PAM) inverter under different excitation angles in both no-load and load conditions. The PAM method automatically controls the amplitude of changeable DC-link voltage, and the excitation angle for switches in the inverter is varied from 120° to 180° according to a 12-step switching pattern designed particularly for the PAM-based inverter of IPMSM. For reference purpose, the pulse-width modulation excitation with a very high voltage modulation index is performed. Various conditions with changes in speed and torque are examined. Experimental results show that harmonic components produced by the PAM inverter in the IPMSM current, voltage and magnetic flux density have large effects on the motor core and copper losses; physics-based explanations and insights are also presented. The PAM under 135° excitation angle has an excellent performance in reducing IPMSM core and copper losses since it can significantly decrease the harmonic components in motor current, voltage and magnetic flux density. Furthermore, simulations using the finite element method are conducted to validate the experimental results of IPMSM core loss with the PAM excitations.

Magnetic Field Characteristics and Stator Core Losses of High-Speed Permanent Magnet Synchronous Motors

This study focuses on the core losses in the stator region of high-speed permanent magnet synchronous motors, magnetic field characteristics in the load region, and variations in iron losses caused by changes in these areas. A two-pole 120 kW high-speed permanent magnet synchronous motor is used as the object of study, and a two-dimensional transient electromagnetic field-variable load circuit combined calculation model is established. Based on electromagnetic field theory, the electromagnetic field of the high-speed permanent magnet synchronous motor under multi-load conditions is calculated using the time-stepping finite element method. The magnetic field distribution of the high-speed permanent magnet synchronous motor under a multi-load condition is obtained, and the variations in iron core losses in different parts of the motor under multi-load conditions are further analyzed. The calculation results show that most of the stator iron core losses are dissipated in the stator yoke. The stator yoke iron loss under the no-load condition exceeds 70% of the total stator iron core loss. The stator yoke iron loss under rated operation conditions exceeds 50% of the total stator iron core loss. The stator loss under rated load operation conditions is higher than that under no-load operation. These observations are sufficient to demonstrate that the running status of high-speed motors is closely related to the stator iron losses, which have significance in determining the reasonable yoke structure of high-speed and high-power motors and the cooling methods of motor stators.

Comparative Study on Single Pulse and Dual Pulses Variable Width Control Strategies for High-Speed PM BLDC Motor Drive

Pulse width modulation (PWM) of voltage source inverter (VSI) is common for speed regulation of permanent magnet (PM) brushless direct-current (BLDC) motor drives. However, when the motor runs at high speed, the conventional PWM technique may become unfeasible due to the low carrier ratio of inverter, which makes the motor current distorted and the motor core loss increased significantly. In this paper, two control strategies, namely single pulse variable width (SPVW) and dual pulses variable width (DPVW), are introduced for the high-speed PM BLDC motor drives, and are comprehensively investigated. Finite element method (FEM) is employed to evaluate and compare the drive system performance when using the conventional PWM, and the proposed SPVW and DPVW, respectively. Influence of the control techniques, especially on the loss distribution, is revealed.

Core Loss Estimation in Electric Machines With Flux-Controlled Core Loss Tester

The complexity of core loss estimation is a serious challenge in the design of high-efficiency electric machines. Current estimation methods based on the Steinmetz equation and loss separation are not accurate enough, even at the rated conditions. This paper describes a loss estimation technique combining finite-element analysis (FEA) and actual core loss measurements. First, flux density waveforms in various parts of the electric machine are determined using FEA. Second, the same waveforms are generated in a wound toroidal core made of the same material as used in the machine. The loss is measured per unit mass, and then the total motor core loss is calculated by integrating the measured W/kg loss values for predefined sections of the motor. These estimation results are compared with those of the Bertotti method. The proposed procedure is shown to improve the accuracy of loss estimation.

Investigation of Increased Ohmic and Core Losses in Induction Motors Under Voltage Fluctuation Conditions

One of the most widely used machines in the industrial systems is induction motor which is likely exposed to various power quality disturbances. This paper investigates the response of three-phase induction motors to instantaneous supply voltage fluctuations. Two-dimensional finite element method is utilized to address the effect of supply voltage fluctuations on the ohmic and core losses of induction motors. In this modelling approach, the effects of nonlinear characteristics of the core materials and stator and rotor slotting are taken into account. It is shown that the presence of voltage fluctuations in the terminals of induction motors produces multiple extra components in the stator and rotor currents and can result in increased losses and heating. The simulation results are validated by measurements of a laboratory test set-up.

Analysis of interlocking performances on non-oriented electrical steels

In order to reduce energy loss in motor, applications of high-efficiency non-oriented electrical steel sheets and optimal laminating process are both important elements. The motor core loss deterioration is influenced by a number of factors, such as flux distribution, stress and strain, space harmonics, temperature, and short circuits between lamination. In conventional clamping method, steel sheets are laminated via interlocking or welding in general manner. The measured energy loss by welding was much larger than that by interlocking. Therefore, interlocking is well known and usually employed with benefit of easy conducting. The protuberance shapes affected the fastening strength. Generally, the intensity of rectangular type is stronger than the circular counterparts. However, the circular interlocking has better magnetic characteristics. To clarify the method effectiveness, interlocking performances regarding fastened strength and magnetic deterioration by lamination were investigated. The key parameters of protuberance shape and forming depth were designed. Precisely manufacturing operation was applied to avoid interlocking failure. Magnetic properties largely influenced by clamping method are crucial to minimizing the magnetic deterioration during laminating procedure. Several experiments for various processing conditions were undertaken, and the quantification results showed the rectangular interlocking had better fastened strength but worsened iron loss comparing with the circular arrangement. To acquire the comprehensive mechanical and electrical identities for electrical steel lamination, deliberate producing conditions regarding minimizing the magnetic deterioration should be adopted prudently.

Effect of armature reaction on the core losses of the permanent magnet synchronous motor

Traditionally, the core losses of permanent magnet synchronous motors are assumed to vary as a function of rotational speed and the supply voltage. In this paper, the effect of armature reaction on the core losses under constant speed and stator voltage is studied. The load angle of the machine is varied, and the core losses are determined using the finite element analysis. To explain the core loss results, the flux densities with harmonic analyses in different parts of the machine are studied and discussed. It is found out that armature reaction should be taken into account if a high-accuracy core loss prediction is required.

Core Loss Computation in a Permanent Magnet Transverse Flux Motor With Rotating Fluxes

This paper presents the core loss computation in a permanent magnet transverse flux motor (TFM) with soft magnetic composite stator core and mild steel rotor yoke, in which the magnetic fluxes rotate. The computation is based on modified core loss models and finite element magnetic field analysis (FEA). The coefficients for the core loss models are obtained by curve-fitting measurements on samples, and the magnetic flux density patterns in the motor are obtained by time-stepping FEA while operating conditions are considered. The computations of the motor core losses agree with the measured values on the TFM prototype. Index Terms—Core loss, finite element analysis, rotating magnetic flux, soft magnetic composite, transverse flux motor.

Losses Characterization in Voltage-Fed PWM Inverter Induction Motor Drives Under Rotor Broken Bars Fault

In this paper, a new analytical methodology is proposed to estimate core losses in line-start and inverter-fed induction motors under rotor broken bars. This methodology can be utilized for different supply and load conditions. Core losses are precisely calculated taking into account the effects of nonsinusoidal distribution of the magnetic flux density due to bars breakage. Furthermore, increase of the stator current side-band components magnitude is considered to estimate Ohmic losses accurately. In order to calculate the above-mentioned losses, distribution of the magnetic flux density and stator currents of the induction motor is simulated using modified winding function method. In this modification, influence of nonlinear characteristics of the core materials is taken into account. Moreover, impacts of the spatial distribution of the stator windings, stator and rotor slots are considered. Two well known CV/F and direct torque control techniques are applied to the modeled motor and the aforementioned losses are calculated in the line-start, and inverter-fed modes. The simulation results are verified by the experimental results.

ChemInform Abstract: Review on Applications of Low Loss Amorphous Metals in Motors

AbstractReview: 20 refs.