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Leakage and fringing flux line trajectories at unaligned and aligned position obtained from a 2D FEM simulations of the SRM prototype.
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A new nonlinear lumped parameter model is proposed for a switched reluctance motor with core losses. The components of the model and their origin are justified by finite element simulations and experimental tests. The winding resistance and the leakage inductance are analyzed by different methods taken from the literature, and a new algorithm is pr...
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... SRM model described in the above section is mainly focused on core loss, but they do not consider the leakage and fringing flux. These effects are appreciated in Fig. 4, which shows the flux line trajectories at aligned and unaligned positions, exhibiting deep flux line dispersion. These results were by using two dimensional (2D) finite element method (FEM) electromagnetic ...
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... a P - P parallel connected network substituting D in Fig. 6. This is shown in Fig. 11, where for convenience it has been transformed into its series equivalent D -ΔR. The new series resistant W =(ΔR+R W ) is named the incremental equivalent winding resistance, where ΔR models the variation shown in Fig. 10. Regarding ΔR, notice that in Fig. 4 and Fig. 5, where FEM simulations are shown, the leakage flux lines flow through the air and the ferromagnetic material, both with a similar reluctance under saturation operation. Therefore, there will be core loss due to the leakage flux. The incremental leakage inductance in (12) can be determined from the leakage flux ...
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... flowchart of this algorithm is depicted in Fig. 13. The procedure is as follows: 1) Initialize W =R W ; 2) Set the array i PH_ALG with the values for phase current i PH used to estimate W and D ; 3) A voltage pulse as in Fig. 9 is evaluated. Fig. 14 shows the leakage flux vs phase current relationship obtained by the proposed algorithm at aligned and unaligned positions (see Fig. 12 The incremental equivalent winding resistance and the incremental leakage inductance determined by the proposed algorithm at aligned and unaligned positions are depicted in Fig. 15. The peak at around ...
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... magnetizing inductance, only the curve representing the increase in the current is considered. The graphical representation of the simulated and the measured signals allows a qualitative evaluation of the model performance (Figs. 21, 22 and 23). In addition, a quantitative evaluation has been carried out using the statistical measures shown in Fig. 24. The results for all the cases are shown in Table ...
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Citations
... A NALYTICAL models are required for initial estimates, design, offline, and real-time simulations, verification of control strategies, and for performance evaluation of electrical machines. The methods of modeling of a switched reluctance motor (SRM) can be broadly classified into three categories namely: 1) finite-element method (FEM) simulations [1], [2], [3], [4], [5]; 2) ψ-i -θ -based approach [6], [7], [8], [9], [10], [11], [12], [13], [14]; and 3) magnetic equivalent circuit (MEC) [15], [16], [17], [18], [19], [20], [21], [22], [23], [24]. SRM being doubly salient and singly excited, none of the existing abovementioned approaches lead to exact/accurate performance prediction. ...
... The MEC-based analysis is another preferred approach due to the rapid simulation [15], [16]. A thorough survey provides novel equivalent circuits [17], [18], [19], [20], methods for computation of air gap permeance/reluctance [21], [22], and development of mesh/node-based equivalent circuits [23], [24]. It is found that the equivalent models are developed on a perphase basis, mostly with reduced geometry (half or one pole pitch), and involve iterative numerical methods to evaluate the large matrices. ...
The paper proposes a new “switched lumped reluctance network” based equivalent circuit for a switched reluctance motor under saturation. The proposed circuit incorporates the effects of the position-dependent switching of the phase windings and changing position of the rotor with respect to the stator. This feature enables the analysis of non-uniform and dynamic variation of flux in motor iron sections along with that in the air-gap and their effects on the phase current. The proposed model thus emulates the operation of a switched reluctance motor, more truly, through an equivalent circuit approach. The accuracy of the proposed model is verified by comparing the analytical results of five different stator-rotor sets (having different air-gap and tooth angular width) with the FEM simulated results and found to be in excellent mutual agreement. The static and dynamic performance obtained using the proposed model has been validated by experiments on a 4 phase, 1 kW, 300 V, 1000 RPM switched reluctance motor.
... However, this is not acceptable for dynamic modelling, according to [17], since the equivalent core-loss resistance in these models does not depend on the magnetising current. In [18,19], a derivation algorithm for the equivalent core-loss resistance dependent on both the angle and the phase current is proposed. However, despite their good performance, these models cover a limited range of the operating regimes of the SRM. ...
... The simulation results show that R phFe , for the same rotor position, is higher at a lower magnetising current and vice versa. In other words, for the observed rotor position, R phFe decreases when the magnetising current increases and vice versa [17,18]. Thus, R phFe is a function of both the magnetising current and the rotor position. ...
Abstract To accurately predict motor performance, considering the effects of core losses is of great importance, especially at speeds much higher than the base where the core losses represent a considerable portion of the total drive losses. Neglecting the effects of core losses leads to an error in the switched reluctance motor (SRM) performance prediction. In this study, a previously developed non‐linear SRM model with multiphase coupling is extended by considering the instantaneous effects of core losses on the SRM performance. Using the new model, the nature of these effects is determined. A comparison of the simulation results of the proposed, basic, and finite element method (FEM) model confirms the importance of considering the effects of core losses on motor performance. Besides the FEM model, the accuracy of the proposed model is verified by experiments.
... Typically, the magnetic properties are included in the equivalent circuit as a magnetizing inductance, representing core magnetization, along with a parallel resistive branch, accounting for core-loss [33], [34]. In most cases core-loss is modeled by a fixed resistance in the equivalent circuit [31], [33], [35]. However, this results in poor modeling accuracy when the machine is experiencing large core loss and saturation [31], [35]. ...
... In most cases core-loss is modeled by a fixed resistance in the equivalent circuit [31], [33], [35]. However, this results in poor modeling accuracy when the machine is experiencing large core loss and saturation [31], [35]. A variable coreloss resistance and magnetizing inductance model, having good accuracy, is proposed in [33]. ...
High speed electric machines operate at tens of thousands of revolutions per minute. The rotor and stator cores experience high frequency electromagnetic fields. While the magnetic characteristics are available at 50/60 Hz, magnetic characteristics are required over a wide range of frequency due to variable speed operation of high speed motor. In this paper tests are carried out on ferromagnetic alloys over a frequency range of 1 Hz to 5 kHz and flux densities ranging from 0.1 T to 2 T. The materials considered include the widely used M36 and 65C600 laminations. In applications where the rotor speed and shaft temperature are high, solid core rotors are more viable than laminated ones. Further, the application requires that the shaft and active magnetic parts of the rotor be made of a single material. Hence, EN353 and EN8 are the prospective rotor materials considered. An extensive experimental study on the magnetic characteristics of these materials over a wide frequency range is reported in this paper. The flux density variation over the core length at different frequencies is analysed using FEA. The results include B-H curves, static magnetisation curves and power loss curves. The loss curves are useful to evaluate the loss density in the magnetic material at different frequencies and for various values of peak flux densities. These experimental data are essential for the analysis, design and performance evaluation of high speed electric machines.
... The starting torque of the 12/8 pole SRM is calculated by the field-circuit coupled finite element method [15][16][17][18][19][20]. The starting torque of SRM means the blockage torque of SRM in this paper. ...
To investigate the influence of control and structure parameters on the starting performance of a switched reluctance motor, a 12/8 pole switched reluctance motor is analyzed in this paper. The novel field-circuit coupled finite element method of switched reluctance motor is proposed in the paper. The influence of the controller on the switched reluctance motor is considered. The influence of rotor initial position angle, starting mode, starting current, and structure parameters on the starting performance of the switched reluctance motor is studied using the field-circuit coupled finite element method. The starting performance of the switched reluctance motor is obtained under the different control and structure parameters. The alternating starting mode of single- and two-phase winding can improve the starting torque of switched reluctance motor (SRM). As the stator pole arc coefficient increases, the starting torque of SRM increases. The appropriate reduction of the air gap length can improve the starting torque of SRM. Experimental results of the prototype are compared with the calculation results, which verifies the reliability of the calculation method and accuracy of the calculation results.
... For RSRM, the equivalent incremental core-loss resistance r lk is related to the rotor position, and the value of r lk at the aligned position is less than that at the fully unaligned position [27], [28]. Similarly, the position information of the PSRM is also reflected by rlk. ...
In this paper, a position estimation method is proposed to realize sensorless control of planar switched reluctance motor (PSRM) with core loss. First, a square-wave voltage generated through bipolar pulse width modulation (PWM) is injected into the idle phase of a PSRM, thereby generating core loss. The corresponding core-loss average power (CLAP), which contains position information, is calculated in real time. Then, depending on the six-phase CLAP, the initial position can be estimated for the PSRM startup. To stabilize the position estimation in different regions of pole pitches, position data measured in a long stroke are utilized to determine a function mapping from the CLAP with respect to position. Furthermore, a sensorless control system and commutation strategy are designed. Finally, the capability of different methods for position estimation and sensorless control of a PSRM system are experimentally investigated. The feasibility and effectiveness of the proposed method are verified through the experimental results.
... The phase winding is usually modeled as a variable magnetizing inductance with series winding resistance [27]. However, for cases of non-negligible iron loss, a coreloss resistance is considered in parallel with the variable magnetizing inductance [24], [29], [30]. Solid-rotor SRM is expected to have significant eddy current effects and core loss. ...
... A constant core-loss resistance is generally used [24]. However this does not ensure unique ψ − i m characteristics [30]. Another method is proposed in [30], where a current dependent resistance is used to establish uniqueness; however this does not ensure symmetry. ...
... However this does not ensure unique ψ − i m characteristics [30]. Another method is proposed in [30], where a current dependent resistance is used to establish uniqueness; however this does not ensure symmetry. Unlike the laminated rotor SRM which has a unique ψ − i characteristics at a given rotor position, the ψ − i loop varies with the applied voltage waveform, even at the same rotor position. ...
Solid-rotor switched reluctance machines (SRM), having rotor machined from single piece of metal, is one of the few viable options for motoring and/or generation under harsh operating conditions including high speeds, high shaft temperature and corrosive environment. Apart from double saliency and high degree of magnetic saturation as in any SRM, significant core losses due to high eddy currents even under static condition make the characterization and modeling of solid-rotor SRM challenging. The objective here is to understand the magnetic characteristics of a solid-rotor SRM through extensive experimental studies and to develop a stator-side model for the machine which adequately captures its magnetic behavior. Firstly, the flux linkage characteristics of the solid-rotor SRM under test are measured over a wide range of excitation conditions and rotor positions. Applying a computationally efficient decomposition technique on each set of experimental data, the measured winding current is resolved into magnetizing and core-loss components to obtain a stator-side model of the machine. The proposed model is useful to predict the winding current and core-loss under different excitation conditions, which is necessary for simulation and performance prediction. The proposed method is more accurate than the existing methods, while being simple and fast to implement.
... Pertaining to SRM, due to its doubly salient structure and non-linearity, the core losses and the windage losses are of key interest to researchers as the characteristics of both these losses in this motor are entirely different from those in AC machines [17]. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] Core losses for an SRM can be estimated based on the magnetic flux density waveforms shown in Fig. 2. Due to the non-linear nature of the flux densities, the losses were quantified through the Fourier series expansion with mathematical models and it was observed that two-thirds of the stator back iron contributed to more than 60% of the total iron loss in the motor [17][18][19][20][21][22]. ...
... Fig. 6 provides a comparison of the measured and computed losses [27][28][29][30]. An equivalent circuit had been developed for the SRM [31][32][33] where the core losses and non-linearity had been accounted as resistance for estimating the core losses, which predicted the losses with 98% accuracy. ...
... Machine details Prominent mitigation strategy Advantages Disadvantages [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] • Core losses short flux path and winding topology • Reduces core loss by 20% • Applicable only to stators greater than ten slots zero voltage loop commutation • 43% reduction in core loss • Optimisation of the turn off time in accordance to the natural vibration frequency of the stator makes its implementation difficult [36][37][38][39][40][41][42][43][44][45] ...
Some key features to be satisfied by electric motors catering a wide range of applications are high specific power, lower manufacturing cost, rugged construction, and fault‐tolerant operation. Switched reluctance motor is one such motor technology satisfying all the above requirements and is an emerging competitor to the induction and permanent magnet motors in domestic, industrial and electric vehicle applications. The present‐day research on this motor is moving towards improving efficiency at lower speeds, power density, and the torque density. Certain challenges in achieving the same are (a) minimising the losses, (b) mitigation of torque ripple, noise, and vibration, and (c) material advancements. A review based on the estimation and mitigation techniques of each of these over the past three to four decades has been dealt with in this study. The salient features and results in each section provide a clear understanding of how each of these challenges can be overcome in the aspect of design and control strategies.
... System simulation Complexity is the significant feature of SRM drive much more than AC & DC motor drives because its operational region nonlinearity. The nonlinearity is produced due to the three factors [6], [7]. First, nonlinearity of B-H characteristics of the magnetic material. ...
Magnetization characteristics play a design significant role, implementation and switched reluctance motors SRMs performance that are considered fault tolerant motors. The first objective in modelling of SRM is to provide a high accuracy and robust operation through the complete speed and torque range. This paper presents physical phenomenon that need to be involved in actual SRM drive model. The introduced method is applied on SRM that may be used in aerospace, military, and medical applications for flux linkage characteristics measurement and consequently inductance. Laboratorial results are well satisfactory, and accurate for implemented SRM modelling and performance analysis. The cost is minimized in flux linkage measurement, and inductance characteristic, where the laboratorial instruments used in this procedure are widespread, and the test bench is easy to build, as the SRM has been built. The test denotes the measuring procedure is simple, and the results are satisfactory, and accurate.
... System simulation Complexity is the significant feature of SRM drive much more than DC & AC motor drives because its operational region nonlinearity. The nonlinearity is produced due to the three factors [6], [7]. First: nonlinearity of B-H characteristics of the magnetic material. ...
Magnetization characteristics play an important role in design, implementation and performance for switched reluctance motors SRMs. The first objective in modelling of SRM is to provide a good accuracy and robust operation over the entire speed and torque range. This paper introduces physical phenomenon that need to be included in actual model of the SRM drive. The introduced methodology is applied on SRM that may be used in aerospace, military, and medical applications for measurement of flux linkage and inductance characteristics. Experimental results are well accurate for modelling and performance analysis of implemented SRM. The cost is lowered in measurement of flux linkage, and inductance characteristic, where the experimental instruments used in this method are common, and the test bench is easy to build, as the SRM has been built. The test indicates the measuring process is simple to implement, and the results are satisfactory, and accurate.
