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Thanks to the absence of rotor windings and permanent magnets, switched reluctance motors have a small weight construction. The integration of a modular power converter in a switched reluctance motor leads to a highly compact and fault-tolerant motor drive with small weight and high power density. In this article, a polygon-retrofitted integration topology is proposed for switched reluctance motors. Both the switched reluctance motor and the power converter are cooled with one shared cooling circuit. The power converter is designed and implemented using silicon carbide technology for its low losses and small thermal resistance. The proposed integration topology is extensively studied using multiphysics modeling and experimental measurements on a fully integrated rotating setup. A highly compact and power dense drive of 3.1 kW/L is obtained. [ABSTRACT FROM AUTHOR]

Most permanent magnet (PM) loss studies consider only eddy current loss and neglect hysteresis. In this article, the hysteresis behavior of two NdFeB PM grades with different magnetic properties is assessed when applied in a PMSM. Data from vibrating sample magnetometer measurements and hysteresis modeling are used as a base. In addition to the main magnetic phase, the samples contained magnetic phases with reduced coercivity. Such phases may contribute to hysteresis losses in a PM material. A new model is introduced to simulate the hysteresis of rare-earth magnets of any geometric shape in the second and first quadrants of the intrinsic BH-plane. The magnetic field strength distribution in the PM material of an electrical motor is analyzed by two-dimensional finite-element method. The results are used as the input data for an analytical hysteresis model. The results indicate that the hysteresis loss resulting from the structural imperfections and geometry of the magnet may introduce a considerable loss in NdFeB PMs applied in rotating electrical machines. [ABSTRACT FROM AUTHOR]

In this article, a circumscribing polygon integrated modular motor drive topology with shared cooling for the power converter and the electrical machine is proposed and benchmarked with the nonintegrated version. The proposed topology is applied on an axial flux permanent magnet synchronous machine. The topology is capable of mechanically mounting the power converter, sufficiently cooling both the power converter and the electrical machine, and combining both of them into the same housing. The mechanical and the thermal design are done to ensure thermal decoupling between the power converter and the motor winding, and to provide a low thermal resistance from the power converter and the electrical machine to the ambient. Due to the limited space available for the power converter module, wide bandgap semiconductor technology is chosen for the implementation of the converter module, thanks to their small package size and low power losses. A highly modular, integrated, and compact drive is achieved compared to the nonintegrated one. A computational fluid dynamics (CFD) model is developed for one module of the proposed integrated drive to evaluate the maximum current that can be injected by one converter module without exceeding the junction temperature limit of the switches and the maximum winding temperature. An experimental setup is built to validate the results of the introduced multiphysics models. [ABSTRACT FROM AUTHOR]

This paper proposes a method to design an electrical variable transmission (EVT) of which the stator and inner rotor contain a distributed three-phase winding, and the outer rotor is equipped with permanent magnets and a dc-field winding. The main problem with the design of EVTs is that the modeling relies on time-consuming finite-element (FE) calculations. Studying the effect of design changes is, therefore, a cumbersome task. To minimize the need for FE calculations, scaling laws are applied, which reduce the computational effort to a matter of milliseconds per design. Therefore, the losses of multiple scaled designs can be analyzed for a given load cycle while taking constraints into account such as maximum torque. By presenting this data in a performance map, the optimal design regarding the losses is easily deduced. To validate the presented methodology, FE calculations, measurements, and available literature are used. [ABSTRACT FROM AUTHOR]

This paper presents a simple and efficient magnetic equivalent circuit (MEC) model for surface axial flux permanent magnet synchronous machines. The MEC model is used to solve all the electromagnetic properties of the machine including the no load, full load voltages, cogging torque, torque ripple, and stator iron core losses. Moreover, this approach can be extended for all surface permanent magnet synchronous machines. The main novelty of this approach is the development of a static system, which accounts for the rotation. The model takes into account the rotor rotation via time-dependent permanent magnet magnetization sources. The static system matrix facilitates a very fast solving. In addition, to take into account the three-dimensional (3-D) effect, a multislicing of the machine in the radial direction is done. This boosts the simulation time to only 60 s for six slices and 50 time steps including the nonlinear behavior of the stator elements with a great accuracy. Additionally, the number of elements in the MEC can be adjusted to reduce the computational time. This model is verified by means of 3-D and two-dimensional (2-D) multislice finite-element models. In addition, experimental validations are also provided at the end. [ABSTRACT FROM AUTHOR]

A new structure of a linear switched reluctance motor is proposed in this paper. With the permanent magnet inserted in the movers, the performance of the original motor is improved. An electromagnetic analysis is done by using the finite element analysis. The influence of the permanent magnets in different positions of the movers on the electromagnetic force is investigated. Furthermore, a theoretical analysis is made, based on the Schwarz–Christoffel transformation and the Maxwell stress tensor method. The mathematic model is also made with the consideration of the end effect and the cogging effect. The theoretical result of the electromagnetic force is compared with the simulation result. The comparison shows that the error is limited. The analysis of the flux, the magnetic field, and the inductance is then made. The results confirm that the new structure makes the motor more linearized. The new structure of linear switched reluctance motor can contribute to reducing the ripple in the electromagnetic force. [ABSTRACT FROM AUTHOR]

A continuous demand for more efficient and more compact drives is pushing the popularity of high-speed permanent magnet synchronous machines (PMSMs). However, high rotational speeds and extreme power densities imply that an appropriate cooling of the rotor may be difficult. This is all the more important because of the risk of demagnetization when permanent magnets are operated at high temperatures. Therefore, it is paramount to reduce the losses in the rotor of high-speed machines as much as possible. One technique to reduce the eddy-current losses is introducing a shielding cylinder, i.e., a conductive sleeve that is wrapped around the magnets. However, when badly designed, such a shielding cylinder may increase, rather than decrease, the losses. Therefore, an in-depth study of the effect of the shielding cylinder on the eddy-current losses in high-speed PMSMs is required. By studying how the eddy-current losses are affected by the shielding cylinder’s thickness and its conductivity, this paper aims at providing more insight in how the eddy-current losses can be reduced. Moreover, the study of the eddy-current losses is repeated for different stator sources to evaluate the importance of accounting for the actual control strategy during the machine’s design. [ABSTRACT FROM AUTHOR]

Despite the use of state-of-the-art thermal modeling tools in the design stage, the measured thermal behavior of prototype electrical machines can differ significantly from the modeled ones. This paper shows how a thermal model, based on the finite-element method, of an electric machine can be improved using inverse modeling techniques. In a thorough study, a forward high fidelity finite-element thermal model of a 4-kW axial flux permanent magnet (PM) machine is introduced and improved using inverse modeling techniques via noncollocated thermal sensors. Parametric model order reduction of the high fidelity finite-element thermal model based on the moment matching method is performed to make the recovery of the actual thermal parameters characterizing the thermal behavior of the axial flux PM machine tractable. Furthermore, the same reduced order model is used to identify the different power loss components in the machine. Experimental results confirm that the presented two-stage approach is capable of identifying the thermal parameters and losses with high accuracy. [ABSTRACT FROM AUTHOR]

A time-harmonic analytical model is presented for a combined study of demagnetization and rotor eccentricity in single-stator double-rotor axial flux permanent magnet synchronous machines (AFPMSM). Demagnetization defects are modeled by scaling the magnetization “square wave” by magnetization factors for each individual magnet on both rotors. Static, dynamic, and mixed rotor eccentricities are modeled using a permeance function. The original contribution of the model is that asymmetrical defects in the two air gaps of the machine can be described with acceptable accuracy and limited additional calculation time. The model is validated with a finite element method and experiments in both healthy and defected operations. Because the model has a short computation time, it is useful for real-time condition monitoring of any AFPMSM with double air gap and either concentrated or distributed windings. [ABSTRACT FROM PUBLISHER]

An electrical variable transmission (EVT) is an electrical machine consisting of a stator and two concentric rotors. It is a competitive alternative for power split devices used in current series–parallel hybrid electric vehicles (HEVs). Although tending to have high power densities, permanent magnet (PM) machines suffer from no-load iron losses. Since the torque interaction between stator and outer rotor is low during large time intervals, the EVT in this paper possesses a flux bridge with dc-field winding to modulate the stator field, while maintaining the inner rotor flux linkage. In this paper, a torque controller is proposed that optimally combines the stator, dc-field, and inner rotor currents in order to minimize the copper and iron losses in every operating point of torque and speed on both rotors. Also the electromagnetic coupling between both rotors is considered. It turns out that there are two optimal load angles for the stator currents, of which one of the two is dominant depending on speed and torque. The control is tested on a 120 kW prototype EVT, and measurement results are given to illustrate the optimal performance obtained with the proposed torque control. In addition, efficiencies are measured in order to support the statements made concerning the proposed method. [ABSTRACT FROM PUBLISHER]

In this paper, a complete sensitivity analysis of the optimal parameters for the axial flux permanent magnet synchronous machines working in the field weakening region is implemented. Thanks to the presence of a parameterized accurate analytical model, it is possible to obtain all the required parameters of the machine. The two goals of the ideal design are to maximize the power density: P\text{density} and the ratio of maximal to rated speed: n\max/n_r, which is an inductance related parameter keeping the efficiency at the target speed above 90$\%$. Different slots/poles/phases combinations are studied to reveal the optimum combination for each phase. This paper has studied the effect of the ratio of number of stator slots to number of rotor poles on the P\text{density} and n\max/n_r. It is shown that a low value of this parameter results in a better P\text{density} and n\max/n_r. The effect of the outer diameter, and the inner to outer diameter ratio are studied with respect to the two design goals. In addition, a comparison between the finite and the theoretical infinite speed designs is implemented. A complete 3D finite element validation has proven the robustness of the analytical model. [ABSTRACT FROM AUTHOR]

An electrical variable transmission (EVT) can be used as a power splitting device in hybrid electrical vehicles. The EVT analyzed in this paper is a rotating field electrical machine having two concentric rotors. On the outer rotor, permanent magnets (PMs) are combined with a dc-field winding, being the first implementation of its kind. The magnetic field in the machine as well as the electromagnetic torque on both rotors are a function of the q- and d-axis currents of the stator and inner rotor, as well as the dc-field current. To describe and fully understand this multiple-input multiple-output machine, this paper gives an overview of the influence of the different current inputs on the flux linkage and torque on both rotors. Focus is given to the hybrid excitation in the d-axis by combining the dc-field current and the alternating currents. This has the advantage compared to other EVT topologies that unwanted stator torque can be avoided without stator d-axis current flux weakening. Results of the analysis are presented by means of the torque to current characteristics of a double rotor PM-assisted EVT, as well as the torque to current ratios. The machine characteristics are finally experimentally verified on a prototype machine. [ABSTRACT FROM PUBLISHER]

The aim of this paper is to calculate the static eccentricity (SE) of a double rotor axial flux permanent magnet (AFPM) machine by using a general analytical model. The flux density in the air gap under healthy conditions is calculated firstly, where the axial and circumferential magnetic flux densities are obtained using a coupled solution of Maxwell's equations and Schwarz-Christoffel (SC) mapping. The magnetic flux densities under SE conditions are calculated afterwards using a novel bilinear mapping. Some important electromagnetic parameters, e.g., back electromotive force (EMF), cogging torque and electromagnetic (EM) torque, are calculated for both SE and healthy conditions, and compared with the finite element (FE) model. As for the double rotor AFPM, SE does not contribute much effect on the back EMF and EM torque, while the cogging torque is increased. At each calculated section, FE models were built to validate the analytical model. The results show that the analytical predictions agree well with the FE results. Finally, the results of analytical model are verified via experimental results. [ABSTRACT FROM AUTHOR]

A comparison between different analytical and finite-element (FE) tools for the computation of cogging torque and torque ripple in axial flux permanent-magnet synchronous machines is made. 2D and 3D FE models are the most accurate for the computation of cogging torque and torque ripple. However, they are too time consuming to be used for optimization studies. Therefore, analytical tools are also used to obtain the cogging torque and torque ripple. In this paper, three types of analytical models are considered. They are all based on dividing the machine into many slices in the radial direction. One model computes the lateral force based on the magnetic field distribution in the air gap area. Another model is based on conformal mapping and uses complex Schwarz Christoffel (SC) transformations. The last model is based on the subdomain technique, which divides the studied geometry into a number of separate domains. The different types of models are compared for different slot openings and permanent-magnet widths. One of the main conclusions is that the subdomain model is best suited to compute the cogging torque and torque ripple with a much higher accuracy than the SC model. [ABSTRACT FROM AUTHOR]

An electrical variable transmission (EVT) is an electromagnetic device with dual mechanical and electrical ports. In hybrid electric vehicles (HEVs), it is used to split the power to the wheels in a part coming from the combustion engine and a part exchanged with the battery. The most important feature is that the power splitting is done in an electromagnetic way. This has the advantage over mechanical power splitting devices of reduced maintenance, high efficiency, and inherent overload protection. This paper gives a conceptual framework on how the torque on both rotors of the EVT can be simultaneously controlled by using a field-oriented control (FOC) scheme. It describes an induction-machine-based EVT model in which no permanent magnets are required, based on classical machine theory. By use of a predictive current controller to track the calculated current reference values, a fast and accurate torque control can be achieved. By selecting an appropriate value for the flux coupled with the squirrel-cage interrotor, the torque can be controlled in various operating points of power split, generation, and pure electric mode. The conclusions are supported by simulations and transient finite-element calculations. [ABSTRACT FROM PUBLISHER]

This paper presents an analytical solution of the eddy currents in the permanent magnets (PMs) in the axial flux PM synchronous machine using a coupled solution of Maxwell’s equations and electric circuit network. This is based on calculating the axial field in an accurate way on the surface of the PM. This method is able to consider the effect of armature field and slots. The eddy currents are obtained by imposing this solution on the PM which is modeled by a simple electric network. This network is composed of simple resistances and inductances. The inductances are used to model the reaction field effect of the eddy currents flowing through the PM and also the skin effect. To show this effect, the machine is excited with different sources at different speeds. In addition, a variant of the model is made that neglects the inductances, in order to show in which conditions this low-frequency approximation is acceptable. It is concluded from this paper that inclusion of the reaction field is necessary when the machine is excited by a pulsewidth modulated (PWM) current, while for a sinusoidal excitation, the reaction field effect has minor contributions to the total eddy losses. In addition, the reaction field has major influence at higher speeds rather than lower speeds for PWM injection. In conclusions, for a preliminary design, the resistance model without the reaction field computation would be enough for the calculation of the PM losses. The circuit model is also capable of obtaining the solution with PM segmentation. In this paper, different PM segments were studied from the circuit model and the finite-element (FE) model point of view. Compared with the FE model, the circuit model has the advantage of flexibility in geometrical machine parameters, less CPU time, and accurate results for the PM losses up to 10%. [ABSTRACT FROM AUTHOR]

This paper presents a complete analytical model for surface-mounted permanent magnet synchronous machines (PMSMs). A new simple and fast technique was developed to obtain accurate results in the calculation of machine parameters electromotive force (EMF), torque, and losses. This technique is based upon the combined solution of two models. The first model generates an exact solution of Maxwell’s equations in the air gap area applied to a very simple geometry. The second model gives an accurate solution in the detailed parts with complex geometry, based on a magnetic equivalent circuit (MEC) to obtain fast and accurate results in a simple way. The machine’s global quantities are then obtained and validated using the results of a finite element model (FEM) for different loading conditions and geometries. Compared with FEM, the proposed combined solution has the advantage of flexibility in the geometrical machine parameters, significantly less CPU time and an accuracy for the considered PMSM up to 4.85% in the EMF, 4.41% in the torque, and 4.44% in the iron losses. Finally, the relation between grid refinement in the MEC (coarse or fine grid of reluctances) and accuracy is pointed out, showing that the EMF can be accurately computed with a rather coarse grid, while accurate loss computation requires a fine grid. [ABSTRACT FROM AUTHOR]

This paper presents an analytical method for permanent magnet demagnetization detection in an axial flux permanent magnet synchronous machine. First, a forward model is built to calculate the three phase terminal voltages with inputs of three phase currents, the geometry of the machine, and the electromagnetic properties of the machine. To model the demagnetization fault, the scalar potential equation is solved. The magnetization waveform is a square wave corrected with magnetization factors that represent the individual magnetization of every magnet. Second, the forward model is inverted so that the magnetization factors are computed out of the three phase currents and the three phase terminal voltages. The forward model is validated with experimental data and finite element simulations. [ABSTRACT FROM AUTHOR]

The efficiency of permanent-magnet (PM) synchronous machines with outer rotor and concentrated windings is investigated as a function of the mass of magnets used, keeping the power, volume, and mechanical air-gap thickness constant. In order to be useful for electric vehicle motors and wind turbine generators, the efficiency is computed in wide speed and torque ranges, including overload. For a given type and amount of magnets, the geometry of the machine and the efficiency map are computed by analytical models and finite-element models, taken into account the iron loss, copper loss, magnet loss, and pulsewidth-modulation loss. The models are validated by experiments. Furthermore, the demagnetization risk and torque ripple are studied as functions of the mass of magnets in the machine. The effect of the mass of magnets is investigated for several soft magnetic materials, for several combinations of number of poles and number of stator slots, and for both rare earth (NdFeB) magnets and ferrite magnets. It is observed that the amount of PM material can vary in a wide range with a minor influence on the efficiency, torque density, and torque ripple and with a limited demagnetization risk. [ABSTRACT FROM PUBLISHER]

For electrical machines with a 3-D geometry, such as axial flux permanent magnet machines, the computation of iron and magnet losses in the case of pulsewidth modulation (PWM) supply could be performed by a transient 3-D finite element model (FEM) coupled with an electrical circuit. To reduce the CPU time, in this paper, these losses are computed with acceptable accuracy without using a 3-D transient FEM. The multislice technique is used with a 2-D static FEM, combined with a state space model of the machine. A Preisach hysteresis model is considered to evaluate the iron loss during minor loops. The loss in the electrical steel and in the magnets is evaluated for several PWM frequencies as well as for different segmentations of the magnets. [ABSTRACT FROM AUTHOR]

Due to their high efficiency and power density, permanent magnet synchronous machines (PMSMs) operating at high speed have recently gained a lot of attention. The development of high-speed PMSMs requires a good understanding of the physics related to the operation of such machines. Moreover, accurate modeling tools are needed when designing high-speed electrical machines. In this paper, the subdomain modeling technique is used to analytically compute the magnetic field of an electrical machine. The idea behind this technique is to divide the machine in a number of subdomains, in which the problem is simplified. The solutions in the different subdomains are then linked by imposing physical boundary conditions. The described model immediately considers the slotting effect and the eddy-current reaction field of a shielding cylinder (SC). The SC is a conductive sleeve, which is wrapped around the magnets. Its goal is to reduce the rotor losses at high-speed operation. This paper starts by introducing the applied modeling technique and the studied machine. Second, the basics of the model and its development are discussed. Finally, the results are compared with results of a finite-element (FE) model. A very good agreement between the proposed model and the FE model is observed. This implies that the developed model is indeed a powerful modeling tool for high-speed PMSMs. Moreover, it provides great insight in the machine’s physics as well. [ABSTRACT FROM PUBLISHER]

SUMMARY The stray field outside outer rotor permanent magnet synchronous motors can be used for rotor position detection. The focus of the research is on the optimal position of the sensors in order to provide accurate rotor position information. By using 2D and 3D models, the effect of the radial, circumferential and axial position of the sensors on the output signal is shown. Furthermore, the effects of the rotor yoke thickness and the stator current are studied: a thick rotor yoke obviously reduces the stray field amplitude, and high stator currents slightly shift the switching points of the Hall sensors, making the position information less accurate. Also, the rotor temperature and the orientation of the sensors towards the direction normal to the rotor surface are important: modifying the orientation causes a phase shift and is a way to tune the sensors without changing the position. Experiments show that an accurate brushless DC control is possible based on Hall sensors in the stray field. The motor and brushless DC control are used for a wheel drive of an ultra-light electric vehicle. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Laminated soft magnetic steel is very often used to manufacture the stator cores of axial-flux PM machines. However, as the magnetic flux typically has main components parallel to the lamination plane, different magnetic flux density levels may occur over the radial direction: High flux densities near the saturation level are found at the inner radius, while the laminations at the outer radius are used inefficiently. To obtain a leveled magnetic flux density, this paper introduces a radially varying air gap: At the inner radius, the air gap is increased, while at the outer radius, the air gap remains unchanged. This results in equal flux densities in the different lamination layers. As the total flux in the stator cores is decreased due to the variable air gap, the permanent-magnet thickness should be increased to compensate for this. The effect of a variable air gap is tested for both a low-grade non-oriented and a high-grade grain-oriented material. For both materials, the redistribution of the magnetic flux due to the variable air gap results in a significant decrease of the iron losses. In the presented prototype machine, the iron losses are reduced up to 8% by introducing a variable air gap. Finally, a prototype machine is constructed using an efficient manufacturing procedure to construct the laminated magnetic stator cores with variable air gap. [ABSTRACT FROM AUTHOR]

On the rotors of an axial-flux PM machine, NdFeB permanent magnets (PM) are very often placed because of their high energy density. As the NdFeB-magnets are good electric conductive, electric currents are induced in the magnets when they are exposed to a varying magnetic field. This varying magnetic field has two causes: variation of the airgap reluctance due to the effect of stator slots and armature reaction due to the stator currents. As axial-flux PM machines have an inherent 3-D-geometry, full 3-D-finite-element modeling seems necessary to calculate the eddy currents in the PM and to evaluate their corresponding losses. In this paper, however, the 1-D airgap magnetic fields of multiple multilayer 2-D finite-element simulations are combined to a 2-D airgap magnetic field using static simulations. In a subsequent step, this 2-D airgap magnetic field is imposed to a 2-D finite-element model of the PM to calculate the eddy currents and eddy current losses. The main benefit of this multilayer 2-D–2-D coupled model compared to 3-D finite-element modeling is the reduction in calculation time. Accuracy of the suggested multilayer 2-D–2-D coupled model is verified by simulations using a 3-D finite-element model. [ABSTRACT FROM AUTHOR]

This paper presents the efficiency study of a 6-pole and 2-pole induction motor (IM), converted into a 6-pole and 2-pole permanent magnet synchronous machine (PMSM). Firstly, the stator of the IM was kept unchanged and the rotor was converted into a permanent magnet (NdFeB magnets) rotor, resulting in higher average efficiency. Secondly, we investigated how much the efficiency can be increased by replacing the electrical steel in the stator by another material grade. The numerical approach is based on the finite element method (FEM), taking into account the rotor movement. Iron losses are computed according to the loss separation theory. From measurements and simulations, it is observed that the efficiency increases significantly compared to the original IM. The average efficiency of the original 1.5 kW IM converted into the 1.5 kW PMSM led to a 14% higher efficiency in a speed range 0.5\Omeganom-\Omeganom and torque range 0.5Tnom-Tnom. When the stator iron is replaced by M235-35A laminations with the same geometry, the average efficiency increases by an additional 2% for the 1.5 kW PMSM with modified stator. [ABSTRACT FROM PUBLISHER]

In this paper, a simple lamination stacking method for the teeth of an axial flux permanent-magnet synchronous machine with concentrated stator windings is proposed. In this simple lamination stacking method, only two lamination profiles are used and are stacked alternately. To evaluate the performance of this stacking method, a comparison is made between the proposed method with two profiles and a conventional stacking method that uses different profiles for each lamination layer, using a multilayer 2-D finite element model. [ABSTRACT FROM PUBLISHER]

The aim of the research is to investigate how much the losses in a permanent-magnet synchronous machine (PMSM) increase by the test pulses that are injected for sensorless control, i.e., to obtain rotor position information without using a position sensor. The current responses to the voltage test pulses in the machine are used as input of a 2-fl transient finite element model (FEM) of the PMSM, to compute the field distribution. The magnet losses are calculated by a 3-D FEM of one magnet and a part of the rotor yoke only. To find the iron losses in the SiFe part of the magnetic circuit, quasi-static and dynamic BH-loops were measured at various amplitudes by using an excitation winding and a measurement winding around the stator yoke of the PMSM. For field waveforms recorded in the 2-D FEM, the corresponding induction is calculated by a static Preisach model. The dynamic field is added based on the theory of loss separation. The test pulses cause minor hysteresis loops. Measurements and simulations show that losses due to the test pulses are usually small and have the same order of magnitude in the permanent magnets and the yoke. [ABSTRACT FROM AUTHOR]

To control the current of a surface mounted permanent magnet synchronous machine fed by a two-level voltage source inverter, a large variety of control algorithms exists. Each of these controllers performs differently concerning dynamic performance and control- and voltage quality, but also concerning sensitivity to demagnetization faults. Therefore, this paper investigates the performance degradation of three advanced predictive controllers under a partial demagnetization fault. The three predictive controllers are: finite-set model based predictive control, deadbeat control, and a combination of both previous algorithms. To achieve this goal, the three predictive controllers are first compared under healthy conditions, and afterwards under a partial demagnetization fault. A PI controller is added to the comparison in order to provide a model-independent benchmark. Key performance indicators, obtained from both simulations and experimental results on a 4 kW axial flux permanent magnet synchronous machine with yokeless and segmented armature topology, are introduced to enable a quantification of the performance degradation of the controllers under a demagnetization fault. A general conclusion is that the deadbeat controller shows superior control quality, even under partial demagnetization. [ABSTRACT FROM AUTHOR]

To find the temperature rise for high power density yokeless and segmented armature (YASA) axial flux permanent magnet synchronous (AFPMSM) machines quickly and accurately, a 3D lumped parameter thermal model is developed and validated experimentally and by finite element (FE) simulations on a 4 kW YASA machine. Additionally, to get insight in the thermal transient response of the machine, the model accounts for the thermal capacitance of different machine components. The model considers the stator, bearing, and windage losses, as well as eddy current losses in the magnets on the rotors. The new contribution of this work is that the thermal model takes cooling via air channels between the magnets on the rotor discs into account. The model is parametrized with respect to the permanent magnet (PM) angle ratio, the PM thickness ratio, the air gap length, and the rotor speed. The effect of the channels is incorporated via convection equations based on many computational fluid dynamics (CFD) computations. The model accuracy is validated at different values of parameters by FE simulations in both transient and steady state. The model takes less than 1 s to solve for the temperature distribution. [ABSTRACT FROM AUTHOR]

In most applications where a variable transmission is required, either an EVT or a CVT would be viable options. In order to obtain a justified decision between both variable transmissions, the operating range and efficiency should be known better. To be able to pinpoint the pros and cons based on efficiency and operating range, a detailed comparison is necessary. However, to the knowledge of the authors there is no such study reported in literature so far. In this paper a permanent magnet Electrical Variable Transmission (EVT) is benchmarked against a half toroidal Continuously Variable Transmission (CVT) and this during steady state conditions. This paper provides the constraints for the comparison and results based on detailed models of both technologies. Two comparative studies are carried out: on one hand a study based on equal maximum output torque and on the other hand a study based on equal rated power. The outcome of the study shows that the CVT is in favor for high input torques and that the EVT is dominant for high input speeds. [ABSTRACT FROM AUTHOR]