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Purpose - The purpose of this paper is to describe how a minimisation of cogging torque is performed with respect to the non-ideal manufacturing process, aiming at a robust design of the studied machine, focusing on magnetisation faults and the use of different qualities of the permanent magnet material. Design/methodology/approach - The applied methodology is a combination of design of experiments and finite element analysis to minimise the cogging torque of the estimated machine. Different qualities of the permanent magnet material are investigated by a stochastic analysis. Findings - A robust design of the machine is achieved, which is verified by a stochastic analysis. Furthermore, this analysis shows the strong influence of the magnet quality on the cogging torque. Practical implications - This paper provides a method for a machine design which is robust against non-ideal manufacturing and an approach to prove the use of a bad quality for a possible reduction of the fabrication costs. Originality/value - This paper gives a close insight on how to investigate non-ideal manufacturing and in particular its influence on the cogging torque.
The invention describes an electrical coil arrangement (21) comprising at least one conductor turn (wi; wl, w2) with two conductor branches (23a, 23b), the first conductor branch (23a) of which is designed as a forward conductor with respect to the prespecified current flow direction and the second conductor branch (23b) of which is designed as a return conductor with respect to this current flow direction. In this case, the individual conductor branches (23a, 23b) are in the form of pressed litz wire conductors which are made stable by a cured filling material (40) and have a large number of electrically conductive individual wires (38), wherein each individual conductor branch (23a, 23b) is formed as a separate, prefabricated conductor segment (27) which is subsequently electrically conductively connected to one another, associated conductor branch (23b, 23a) in at least one end region (17). The invention further describes an electrical machine (1) comprising a coil arrangement (21) of this kind, and a method for producing a coil arrangement (21) of this kind.
he reduction of emission is a key goals for the aviation industry. One enabling technology to achieve this goal, could be the transition from conventional gas turbines to hybrid-electric drive trains. However, the requirements concerning weight and efficiency that come from applications like short range aircraft are significantly higher than what state-of-the-art technology can offer. A key technology that potentially allows to achieve the necessary power and volume densities for rotating electric machines is superconductivity. In this paper we present the concept of a high power density generator that matches the speed of typical airborne turbines in its power class. The design is based on studies that cover topology selection and further electromagnetic, HTS, thermal, structural and cryogenics aspects. All domains were analyzed by means of analytical sizing and 2D/3D FEA modeling. With the help of our digital twin that is a synthesis of these models, we can demonstrate for the first time that under realistic assumptions on material properties gravimetric power densities beyond 20 kW kg−1 can be achieved.
The invention relates to a stator (3) for an electric alternating current machine (1) with a number p of magnetic poles, wherein - the stator (3) has a central axis A, - the stator (3) has a stator winding (4) with a plurality of conductor windings (13j), - the individual conductor windings (13j) are grouped into a total of n electric phases (u, v, w), - the conductor windings (13j) of a phase each have at least a first conductor branch (23a) and a second conductor branch (23b), - said conductor branches (23a, 23b), over most (1) of the length thereof, are arranged in a helical manner around the central axis (A), and - said helically arranged conductor branches (23a, 23b) each have a pitch h greater than the product of the axial length l of the helical conductor branches (13j) and the pole number p. The invention also relates to an electric machine (1) having a stator (3) of this kind.
The invention relates to a stator (3) for an electric alternating-current machine (1) with a number of magnetic poles p, wherein the stator (3) comprises a central axis A, said stator (3) comprises a stator winding (4) with a plurality of conductor windings (13j), a portion (l) of each winding running helically in relation to the central axis (A), and wherein the individual conductor windings (13j) are grouped together to collectively form n phase windings (u1, u2 to w3, w4), characterised in that the number n of the phase windings is higher than three, particularly an integral multiple of three. The invention further relates to an electric machine (1) comprising such a stator (3).
In this paper a phenomenogical energy-based harmonic ferromagnetic material model is presented which considers time-dependent hysteresis losses as a part of the material characteristic. The model is based on the effective reluctivity concept and can be applied to simulate hysteresis losses of electromechanic devices. The hysteresis losses of a C-Core are simulated and compared to the results of an iron loss estimation by loss curves.
In this paper, a phenomenological energy-based material model for ferromagnetic materials under harmonic conditions is presented. The model is based on the concept of a complex effective permeability and an accurate representation of energy is adopted as identification criteria. The material model is implemented in a time-harmonic finite element model, which allows to solve for the loss characteristics of electromagnetic devices. Identification is based on measured hysteresis loops and no additional fitting parameters are required. Hysteresis losses in a ferromagnetic C-core and a ferromagnetic torus are simulated and compared to the results obtained by means of tabulated loss characteristics.
The evaluation of the electromagnetic, structural and acoustic behavior of an induction machine is computationaly expensive. Optimization algorithms are therefore not applicable.
This papers demonstrates that the methodology of design of experiments (Taguchi method) has been successfully applied for the multi-objective optimization of such multiphysics devices. A significant improvement of the machine performances can be achieved with this approach after only a few evaluations of the coupled FE model
Non grain-oriented electrical steel has an inherent anisotropy, which is normally neglected in the calculation of electrical machines. Moreover, the magnetic anisotropy is usually measured in small material samples. Due to the cutting effect, the magnetic anisotropy in the machine is not the same as in the sample. In this paper, the magnetic anisotropy is considered as a global problem. A method to measure it is presented and its influence on the electromagnetic and acoustic behavior is considered through the example of an induction motor.
Non grain-oriented electrical steel has an inherent anisotropy, which is normally neglected in the calculation of electrical machines. Moreover, the magnetic anisotropy is usually measured in small material samples. Due to the cutting effect, the magnetic anisotropy in the machine is not the same as in the sample. In this paper, the magnetic anisotropy is considered as a global problem. A method to measure it is presented and its influence on the electromagnetic and acoustic behavior is considered through the example of an induction motor.
Numerical Calculation of Iron Losses in Electrical Machines with a modified Post-Processing Formula
(2007)
The motivation of this analysis is the need of high efficiency and high power density permanent magnet synchronous motor (PMSM) drives for use in electrical vehicle power trains. It is clear that the chosen electrical steel for the lamination stack plays an important role, but proper quantification is missing. The purpose of this paper is to formalize the problem of selecting the optimal steel grade for the construction of PMSM’s. This question is important to steel producers, not only for helping customers selecting the most appropriate existing grade for their application, but also for defining the strategic orientation of the further R&D of enhanced electrical steel grades. The notion of steel efficiency is defined and, after describing the FE implementation of iron loss models, a methodology for material optimisation is proposed.
Electric Machine (Patent)
(2015)
The invention relates to an electric asynchronous machine (1), in particular an induction machine, comprising: - a cylindrical stator (2) with stator teeth (22) on a stator yoke (21), wherein a ratio between a yoke height (hy1) of the stator yoke (21) in the radial direction and a groove height (hn1) of the stator grooves (23) in the radial direction ranges from 1.75 to 2.5; - a cylindrical rotor (4) with poles (42) on a rotor yoke which are defined by short-circuit windings in a rotor body (41), wherein a ratio between the yoke height of the rotor body (41) in the radial direction and the groove height of the rotor grooves in the radial direction ranges from 2 to 2.75.
The invention relates to a method and a device for operating an externally excited electric machine (1), in particular synchronous machine. In this context, a variable which characterizes a rotor temeperature (Temp_Rotor) and/or a stator temperature is determined using a sensor system, and an exciter current (l_E) and stator currents (l_U, l_V, l_W) for the electric machine (1) are defined by a control unit (3) at least in predefinable operating ranges as a function of the variable which characterizes the rotor temperature (Temp_Rotor) and/or the stator temperature.
The production process of electrical machines is subject to manufacturing and material tolerances. These tolerances have an influence on both, the mean torque and the torque ripple. Consequently, they exert an active influence on the speed-torque map (operating points), as well as the equivalent circuit diagram parameters for a permanent magnet synchronous machine, and the operational behavior (efficiency, noise development) of the electrical machine. In addition to striving lower costs, there is a growing emphasis on achieving higher energy efficiency. Thus, an accurate prediction of machine parameters is still essential during the early development process, despite manufacturing-related deviations.
In this study, the prediction of machine parameters is demonstrated using the example of a PMSM.
The invention relates to a rotor for an electric machine and to a method for manufacturing such a rotor. The rotor (15) comprises a rotor body (9) having a plurality of holes (5) and a plurality of magnets (7) that are accommodated in the holes (5) of the rotor body (9). The magnets (7) are enclosed at least partially by a thermoplastic material and secured by the latter in the holes (5). In comparison to conventional duroplastic adhesives, the thermoplastic materials enable a simpler positive locking securing of the magnets (7) in the rotor body (9). Magnetic or magnetizable particles can be embedded in the thermoplastic material (13), such that a gap (11) between the magnets (7) and the walls of the holes (5), which gap is filled with the thermoplastic material (13), can contribute to the total magnetic field generated by the rotor.
The invention relates to an asynchronous machine (1) as can be used particularly in electric vehicles or hybrid vehicles. The asynchronous machine (1) has a rotor (5) and a stator (3). The asynchronous machine is designed and controlled in such a manner that it has a pole pair number p of p=3. Because of the reduced yoke saturation that can consequently be achieved, the stator yoke (9) can be designed with a lesser height hy1, such that a ratio of the outer rotor diameter D2a to the outer stator diameter D1a can assume values between 0.7 and 0.8. As a result, enlarged rotor teeth (19) and correspondingly enlarged rotor grooves (21) can be formed in the rotor (5), such that electrical losses in the material in the rotor grooves (21) acting as the rotor coil element (23) are smaller in comparison to conventional asynchronous machines. The electrical losses occurring to a greater extent in the stator (3) compensating for this lead to a lesser warming of the stator (3) than would be the case with the rotor (5) as the stator (3) can be cooled by simple means. Overall, a higher continuous torque can thus be achieved with the asynchronous machine (1) according to the invention.