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Woking, United Kingdom

Malloy A.C.,Imperial College London | Martinez-Botas R.F.,Imperial College London | Lamperth M.,GKN EVO eDrive Systems Ltd
IEEE Transactions on Energy Conversion

Magnet losses in permanent magnet synchronous machines (PMSMs) decrease efficiency and increase thermal loading. This paper presents a measurement technique for measuring the magnet losses in PMSMs. Losses were determined by measuring the initial temperature rise rate of the magnets. Measurement of magnet temperature was achieved via a calibration relating temperature rise to voltage constant. Measurements were made on an inverter driven axial flux PMSM at a number of different operating points. The results were used to validate a finite-element analysis, which decomposed the total loss into component parts based on the source of the flux variation in the magnets. The analysis showed that although the magnetomotive force (MMF) induced losses increased with current loading, the harmonic content of the current waveform decreased, leading to only small changes in total loss. Measurements were made at different dc bus voltages; a 60% increase in dc bus voltage increased magnet losses by 32%. © 1986-2012 IEEE. Source

Mlot A.,GKN EVO eDrive Systems Ltd | Korkosz M.,Rzeszow University of Technology | Grodzki P.,Rzeszow University of Technology | Lukaniszyn M.,Opole University of Technology
Przeglad Elektrotechniczny

Accurate prediction of power loss distribution within an electrical device is highly desirable as it allows for thermal behavior to be evaluated at the early design stage. This paper focuses on the ac copper loss caused by circulating current effects in electrical machines. Two different phenomena lead to additional ac losses: skin effect and proximity effect. Skin effect is the tendency for high frequency currents to flow on the surface of a conductor and can be mitigated through the use of small conductor strands. The proximity effect is the tendency for current to flow in other undesirable patterns that form localized current loops or concentrated distribution due to the presence of a magnetic field generated by nearby conductors. To evaluate the ac copper loss within the analyzed machine a simplified approach is adopted utilizing the segmented stator topology. To minimize and show an effect of proximity and/or end-winding on the ac copper loss at presented electrical machine a number of winding arrangement are investigated. Three-dimensional and two-dimensional finite element analysis was applied to calculate a ratio of ac to dc resistant at high frequency sinusoidal current. This resistant ratio demonstrates the amount of copper loss which is increased by high frequency. The resistant ratio is strongly dependent on frequency, temperature and shape of slot and size of slot opening. The theoretical finding is compared against the experimental data of total power losses. Source

Malloy A.C.,Imperial College London | Malloy A.C.,GKN EVO eDrive Systems Ltd | Martinez-Botas R.F.,Imperial College London | Lamperth M.,GKN EVO eDrive Systems Ltd
Energy Conversion and Management

Devices such as rotating electrical machines, transformers, and microprocessors experience thermal loading during operation. This is caused by device losses which manifest themselves as heat sources. Whether operated continuously or on a duty cycle these heat sources are often periodic in nature, exhibiting both mean and fluctuating components. This paper proposes a criterion which can be used to estimate the relative importance of the fluctuating component of a periodic heat source on the temperature response of a device, or a component within a device. It may be used by the heat transfer analyst to determine whether a periodic heat source can be modeled accurately by its mean value or whether it must be modeled as a function of time. During thermometric tests it enables the experimentalist to determine whether the measured temperature rise rate represents an instantaneous or a mean value of heat generation rate. The criterion is derived by considering a sinusoidal heat source acting on a thermal network element. A case study is presented where the criterion is used to estimate the relative importance of the fluctuating component of a range periodic heat sources present in a rotating electrical machine. Results are compared with numerical predictions and agreement is found to be fit for purpose. © 2015 Elsevier Ltd. All rights reserved. Source

Hey J.,Singapore Institute of Manufacturing Technology | Malloy A.C.,GKN EVO eDrive Systems Ltd | Martinez-Botas R.,Imperial College London | Lamperth M.,GKN EVO eDrive Systems Ltd
Energy Conversion and Management

Energy conversion devices undergo thermal loading during their operation as a result of inefficiencies in the energy conversion process. This will eventually lead to degradation and possible failure of the device if the heat generated is not properly managed. The ability to accurately predict the thermal behavior of such a device during the initial developmental stage is an important requirement. However, accurate predictions of critical temperature is challenging due to the variation of heat transfer parameters from one device to another. The ability to determine the model parameters is key to accurately representing the heat transfer in such a device. This paper presents the use of an inverse identification technique to estimate the model parameters of an energy conversion device designed for vehicular applications. To simulate the imperfect contact and the presence of insulating materials in the permanent magnet electric machine, thin material are introduced at the component interface of the numerical model. The proposed inverse identification method is used to estimate the equivalent thermal conductance of the thin material. In addition, the electromagnetic losses generated in the permanent magnet is also derived indirectly from the temperature measurement using the same method. With the thermal properties and input parameters of the numerical model obtained from the inverse identification method, the critical temperature of the device can be predicted more accurately. The deviation between the maximum measured and predicted winding temperature is less than 2.4%. ©2015 Elsevier Ltd. All rights reserved. Source

Lamperth M.U.,GKN EVO eDrive Systems Ltd | Malloy A.C.,GKN EVO eDrive Systems Ltd | Mlot A.,GKN EVO eDrive Systems Ltd | Cordner M.,GKN EVO eDrive Systems Ltd
28th International Electric Vehicle Symposium and Exhibition 2015, EVS 2015

Axial flux (AF) motors and generators have been used in niche automotive applications for many years. Given their disk like shape they offer distinct advantages for integration into hybrid powertrains where available length is limited. An overview of axial machine topologies is given and the design and performance laws that govern the sizing of axial flux permanent magnet machines are presented. Based on the analytical laws described it is shown that an axial machine can achieve significantly more torque than a size comparable radial machine. 3D finite element analysis is used to fine-tune designs and to investigate loss mechanisms. A P2 hybrid module case study is used to show the benefits and challenges of the axial topology when compared to the radial one. The cooling system of the machine is presented in order to show how the integration of coolant passages could be achieved. The possibility of introducing heat barriers into a hybrid powertrain, decoupling the hybrid module from the rest of the powertrain, is also presented. The predicted performance of the machine is presented and compared to the initial test results. Source

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