Lumped Circuit Thermal Model of an Axial Flux Motor (original) (raw)
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Hybrid Cooling Method of Axial-Flux Permanent-Magnet Machines for Vehicle Applications
IEEE Transactions on Industrial Electronics, 2015
Thermal properties are a key issue in many applications associated with electrical machines. Because of its special configuration, an axial-flux electrical machine usually uses self-ventilation. However, this cooling method has a significant impact degrading the machine operating characteristics, and thus, an independent cooling system is desirable. The focus of this paper is on the steady-state thermal modeling and laboratory testing of an axial-flux permanent-magnet (AFPM) electrical machine intended for a traction application. The proposed hybrid cooling arrangement consists of a frame cooling circuit with a water flow inside, a set of copper bars inserted in the teeth, and a segment of potting material around the end windings. Computational fluid dynamics and finite-element analysis are applied for the preliminary design. This paper provides experimental verification of the simulation results on a 100-kW AFPM electrical machine. Index Terms-Electrical machines, hybrid cooling method, liquid jacket, thermal analysis. I. INTRODUCTION A XIAL-FLUX permanent-magnet (AFPM) electrical machines are gaining popularity in electrical vehicles, bicycles, wind power generation systems, and other applications, where high torque density and compact design are required [1]-[6]. An axial-flux machine usually enables inherent selfventilation because of the rotating rotor disks along the whole diameter and an option to arrange multigaps in the rotor body and its support structure to provide higher turbulence, particularly in the two rotors and one stator design [4], [7], which Manuscript
International Journal of Thermal Sciences, 2010
A two dimensional lumped parameter model (LPM) which provides the steady state solution of temperatures within axisymmetric single-sided, slotted axial flux generators is presented in this paper. The two dimensional model refers to the heat modelling in the radial and axial directions. The heat flow in the circumferential direction is neglected. In this modelling method, the solid components and the internal air flow domain of the axial flux machine are split into a number of interacting control volumes. Subsequently, each of these control volumes is represented by thermal resistances and capacitances to form a two dimensional axisymmetric LPM thermal circuit. Both conductive and convective heat transfers are taken into consideration in the LPM thermal circuit by using annular conductive and convective thermal circuits respectively. In addition, the thermal circuit is formulated out of purely dimensional information and constant thermal coefficients. Thus, it can be easily adapted to a range of machine sizes. CFD thermal modelling and experimental testing are conducted to validate the temperatures predicted from the LPM thermal circuit. It is shown that the LPM thermal circuit is capable of predicting the surface temperature accurately and potentially replacing the CFD modelling in the axial flux machine rapid design process.
2010
This paper presents the development of a hybrid thermal model for the EVO Electric AFM 140 Axial Flux Permanent Magnet (AFPM) machine as used in hybrid and electric vehicles. The adopted approach is based on a hybrid lumped parameter and finite difference method. The proposed method divides each motor component into regular elements which are connected together in a thermal resistance network representing all the physical connections in all three dimensions. The element shape and size are chosen according to the component geometry to ensure consistency. The fluid domain is lumped into one region with averaged heat transfer parameters connecting it to the solid domain. Some model parameters are obtained from Computation Fluid Dynamic (CFD) simulation and empirical data. The hybrid thermal model is described by a set of coupled linear first order differential equations which is discretised and solved iteratively to obtain the temperature profile. The computation involved is low and th...
IEEE Transactions on Energy Conversion, 2013
This paper presents a practical approach to model thermal effects in directly cooled electric machines. The main focus is put on modeling the heat transfer in the stator winding and to the cooling system, which are the two critical parts of the studied machines from a thermal point of view. A multisegment structure is proposed that divides the stator, winding, and cooling system into a number of angular segments. Thereby, the circumferential temperature variation due to the nonuniform distribution of the coolant in the cooling channels can be predicted. Additionally, partial computational fluid dynamics (CFD) simulations are carried out to model the coolant flow in the cooling channels and also on the outer surface of the end winding bodies. The CFD simulation results are used as input to the analytical models describing the convective heat transfer to the coolant. The modeling approach is attractive due to its simplicity since CFD simulations of the complete machine are avoided. The proposed thermal model is evaluated experimentally on two directly cooled induction machines where the stator winding is impregnated using varnish and epoxy, respectively. A good correspondence between the predicted and measured temperatures under different cooling conditions and loss levels is obtained. Index Terms-Computational fluid dynamics (CFD), conductive heat transfer, convective heat transfer, directly cooled electric machines, induction machines, lumped parameter (LP) thermal models. NOMENCLATURE A Ch Cooling channel cross-sectional area. A EW End winding ring cross-sectional area of one slot in the axial direction. A EW ,Cu Copper cross-sectional area of the end winding ring in the circumferential direction.
Thermal Analysis of Radial-Flux Electrical Machines With a High Power Density
IEEE Transactions on Industrial Electronics, 2008
A lumped-parameter-based thermal analysis applicable to radial-flux electrical machines with a high power density is presented. The modeling strategies using T-equivalent lumped-parameter blocks as well as conventionally defined thermal resistances are discussed. Special attention is paid to the modeling of the convective heat transfer in the air gap of radial-flux electrical machines at different rotational speeds. A brief overview of the evaluation of different loss components is given. The performance of the developed thermal model was verified by comparing the calculated temperature values with the measurements in three different applications.
IEEE Transactions on Transportation Electrification
For aerospace applications, power density is a major driving force in the design of electrified powertrains. At the forefront is the challenging design of electric motors with high efficiencies, torque, and power capabilities. Due to its high performance, the Axial Flux Permanent Magnet (AFPM) Motor is expected to be one of the leading technologies to meet the demands of these industries. Finding the balance between the cooling system's effectiveness and subsequent parasitic losses is key to utilizing these performance benefits. Single stator double rotor topologies achieve the best torque density and lower stator losses, however are more challenging to cool as the stator is in the center of the motor. Single stator single rotor and double stator machines are less challenging to cool but typically have lower power density. Rotor air cooling is discussed including the effectiveness of blades, meshes, and vents which can be optimized to prevent demagnetization. Stator cooling is critical as many machines maximize current density C. Jenkins,
Energies, 2021
This paper proposes a new construction with a heat sink integrated into the concentrated wound coils of an axial flux, direct liquid cooled electrical machine. A preliminary assessment of the effectiveness of the heat sink and its position is made using computational fluid dynamics. Lumped-parameter thermal models are also developed, thus allowing accurate comparison of the thermal profile of the two constructions. Following experimental calibration of the model and thermal validation, the temperature profile of the new construction is compared to that from a traditional concentrated wound coil. The model is then used to estimate the effect of the new construction on the current density of the stator windings. The paper demonstrates that for an axial flux motor run at a typical operating point of 300 Nm and 1500 rpm, the maximum temperature is reduced by 87 K. The current density can be increased by 140% before the limiting maximum coil temperature is achieved.
Thermal Modeling of a Segmented Stator Winding Design
IEEE Transactions on Industry Applications, 2000
This paper presents a thermal analysis of a segmented stator winding design. As the thermal performance is one of the main factors limiting a machine's output capability, a thermal test on a complete prototype machine is an essential part of the design process. However, for the segmented stator winding design, a test-informed thermal analysis on a single stator tooth can be performed prior to the manufacture of the full machine. This approach allows for a rapid and inexpensive assessment of the thermal performance of the complete machine and early identification of design modifications needed. The research has been applied to the design of a highly efficient and compact permanent-magnet traction motor. A thermal model for a single tooth was developed and supported by tests to identify key heat transfer coefficients. A number of winding assemblies were compared, and the most promising was selected for the final motor prototype. The results from the approach are compared with thermal test results from the complete machine.
Assessment of Axial Flux Motor Technology for Hybrid Powertrain Integration
World Electric Vehicle Journal, 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.