Stator winding short-circuit faults are among the most common faults that could occur in permanen... more Stator winding short-circuit faults are among the most common faults that could occur in permanent magnet synchronous machines (PMSM). Therefore, on-line diagnosis of incipient stator winding short-circuit faults plays an important role contributing to the safe operation of PMSMs. However, the efficacy of known diagnostic methods varies with the types of stator winding configurations in PMSMs. This paper compares the effectiveness of diagnosis of stator winding short-circuit faults in series and parallel winding connections of PMSMs, with the same interior permanent-magnet rotor configuration. Two existing diagnostic methods have been applied to detect the severity of stator short-circuit faults happening in both series and parallel winding connection in PMSMs. Simulation analysis has been carried out in ANSYS Maxwell to compare the severity of magnetic saturation caused by equivalent short-circuit fault in series and parallel winding connected PMSMs. Experimental results lead to the conclusion that PMSMs with parallel winding connections can mask the influence of such stator short-circuit faults under certain circumstances, and thus it is more challenging to detect such incipient faults in parallel-winding-connected PMSM in comparison with series-winding-connected PMSMs.
This paper presents a feasibility study between a design for synchronous reluctance (SyncRel) mot... more This paper presents a feasibility study between a design for synchronous reluctance (SyncRel) motors with integer slots/pole, i.e. 36 slots/4poles and fractional slots/pole, slots per pole ratio higher than 3, i.e. 18 slots/4poles configuration. The analysis is extended also to low energy permanent magnet assisted synchronous reluctance motor (PM SyncRel). It is found that the integer slots/pole solution have a better efficiency for SyncRel, while fractional slots/pole solutions benefit the PM SyncRel design. Potentially, integer slots/pole designs might have higher torque ripple and lower power factor than fractional slots/pole solutions. The presence of very low energy permanent magnets, as bonded plastic ferrite leads to significant increase in the constant torque speed range and power output.
This paper presents the performance trade-offs in the design optimization of spoke-type permanent... more This paper presents the performance trade-offs in the design optimization of spoke-type permanent magnet (PM) motors for high speed and very high torque density traction motors. An example 18-slot 16-pole machine for a direct drive Formula E race car over the Le Mans driving cycle is considered. Both low speed and extended speed/field-weakening operations are evaluated using high fidelity finite element (FE) simulations, to simultaneously increase the torque density and decrease the power losses over the high energy-throughput-zones of the machine torque-speed plane. The results of the design optimization process yielding 3,400 design candidates are utilized to quantify the performance trade-offs for increasing the power density in spoke-type PM motors. These trade-offs include the impacts on other performance metrics such as power losses, PM demagnetization, and torque ripple. The analysis is supplemented by multi-physics simulation of three counterpart optimized designs, and successful experimental verification of a prototype of one of those three designs which represents a record high power density motor in traction applications.
ABSTRACT In this paper, simplified FE-based modeling and analysis of torque ripples in permanent ... more ABSTRACT In this paper, simplified FE-based modeling and analysis of torque ripples in permanent magnet ac machines is presented. The electromagnetic torque is calculated based on the virtual work principle, where field quantities are evaluated using a minimal number of nonlinear magnetostatic finite element solutions. A simple and fast method of incorporating the effects of the stator and/or rotor skew in the torque calculation is introduced. The proposed method requires a minimum number of 2-D finite element evaluations to estimate the electromagnetic torque profile of the skewed machine at a given load condition. This is especially beneficial for rapid evaluation of the effects of stator and/or rotor skew in large-scale design optimization studies. A fast method of evaluating stator tooth forces using a Maxwell stress tensor approach applied to the field quantities calculated using minimum number of 2-D magnetostatic finite element solutions is introduced. Finally, effects of the skew on the developed tooth forces are evaluated.
The conventional scaling rules for the optimal design of electric machines are best suited for na... more The conventional scaling rules for the optimal design of electric machines are best suited for naturally cooled machines with stator winding current densities less than 4A/mm2. In this paper, through a comprehensive sensitivity analysis, first, it is demonstrated that the correlations between some geometric variables and the performance metrics of interior permanent magnet (IPM) motors vary significantly with respect to the stator winding current density. For this purpose, three current densities are selected so as to approximately account for naturally cooled, fan-cooled and liquid-cooled machines. Subsequently, a parameterized IPM motor is optimized at these current densities through a large-scale design optimization algorithm by evaluating a total of 20,000 design candidates. The 100 best designs from each group are then identified and extracted to investigate the scaling rules for the optimal design of such IPM motors with different cooling systems. The outcomes of the study are in correspondence with the conventional design principles for naturally cooled machines. Nevertheless, it is illustrated that these rules vary for fan-cooled and liquid-cooled machines owing to the increased ampere loading, and also heavy saturation of the magnetic core in such machines. A configuration of a 50 hp, 48-slot, 8-pole IPM motor with a single-layer v-type magnet is used as the benchmark of this study.
A novel automated design algorithm for application-based optimization of permanent magnet (PM) ma... more A novel automated design algorithm for application-based optimization of permanent magnet (PM) machines is presented in this paper. The proposed algorithm features precise performance evaluation of the potentially heavily saturated machines at high-energy-throughput operating zones using finite element (FE) techniques. First, the energy consumption function associated with the machine's operating cycle is efficiently modeled by a number of representative load points using a k-means clustering algorithm. Subsequently, a new approach is developed to assess the performance of the machine at each representative load point with proper control to conform to practical operational constraints imposed by voltage and current limits of the motor-drive system. The developed algorithm is applicable to the optimization of any configuration of PM and synchronous reluctance motors over any conceivable operating cycle. Its effectiveness is demonstrated by optimizing the well-established reference/benchmark design represented by the 2004 Toyota Prius IPM motor configuration over a compound operating cycle consisting of common US driving schedules.
This paper describes a systematic method for optimally designing with multiple objectives and dif... more This paper describes a systematic method for optimally designing with multiple objectives and differential evolution (DE) algorithms, current regulated electronically controlled synchronous reluctance (SynRel) machines. A large-scale study with thousands of designs calculated with a ultrafast computationally efficient electromagnetic finite-element analysis (CE-FEA) establishes the performance limitations of conventional radially laminated technology with multiple flux barriers. The potential advantages of employing permanent-magnet (PM)-assisted technology with additional ferrites in the rotor are quantified in terms of substantially improved power factor, specific power, and efficiency. Numerical and experimental results for a 10-hp, 1800-r/min typical rating are included.
Stator winding short-circuit faults are among the most common faults that could occur in permanen... more Stator winding short-circuit faults are among the most common faults that could occur in permanent magnet synchronous machines (PMSM). Therefore, on-line diagnosis of incipient stator winding short-circuit faults plays an important role contributing to the safe operation of PMSMs. However, the efficacy of known diagnostic methods varies with the types of stator winding configurations in PMSMs. This paper compares the effectiveness of diagnosis of stator winding short-circuit faults in series and parallel winding connections of PMSMs, with the same interior permanent-magnet rotor configuration. Two existing diagnostic methods have been applied to detect the severity of stator short-circuit faults happening in both series and parallel winding connection in PMSMs. Simulation analysis has been carried out in ANSYS Maxwell to compare the severity of magnetic saturation caused by equivalent short-circuit fault in series and parallel winding connected PMSMs. Experimental results lead to the conclusion that PMSMs with parallel winding connections can mask the influence of such stator short-circuit faults under certain circumstances, and thus it is more challenging to detect such incipient faults in parallel-winding-connected PMSM in comparison with series-winding-connected PMSMs.
This paper presents a feasibility study between a design for synchronous reluctance (SyncRel) mot... more This paper presents a feasibility study between a design for synchronous reluctance (SyncRel) motors with integer slots/pole, i.e. 36 slots/4poles and fractional slots/pole, slots per pole ratio higher than 3, i.e. 18 slots/4poles configuration. The analysis is extended also to low energy permanent magnet assisted synchronous reluctance motor (PM SyncRel). It is found that the integer slots/pole solution have a better efficiency for SyncRel, while fractional slots/pole solutions benefit the PM SyncRel design. Potentially, integer slots/pole designs might have higher torque ripple and lower power factor than fractional slots/pole solutions. The presence of very low energy permanent magnets, as bonded plastic ferrite leads to significant increase in the constant torque speed range and power output.
This paper presents the performance trade-offs in the design optimization of spoke-type permanent... more This paper presents the performance trade-offs in the design optimization of spoke-type permanent magnet (PM) motors for high speed and very high torque density traction motors. An example 18-slot 16-pole machine for a direct drive Formula E race car over the Le Mans driving cycle is considered. Both low speed and extended speed/field-weakening operations are evaluated using high fidelity finite element (FE) simulations, to simultaneously increase the torque density and decrease the power losses over the high energy-throughput-zones of the machine torque-speed plane. The results of the design optimization process yielding 3,400 design candidates are utilized to quantify the performance trade-offs for increasing the power density in spoke-type PM motors. These trade-offs include the impacts on other performance metrics such as power losses, PM demagnetization, and torque ripple. The analysis is supplemented by multi-physics simulation of three counterpart optimized designs, and successful experimental verification of a prototype of one of those three designs which represents a record high power density motor in traction applications.
ABSTRACT In this paper, simplified FE-based modeling and analysis of torque ripples in permanent ... more ABSTRACT In this paper, simplified FE-based modeling and analysis of torque ripples in permanent magnet ac machines is presented. The electromagnetic torque is calculated based on the virtual work principle, where field quantities are evaluated using a minimal number of nonlinear magnetostatic finite element solutions. A simple and fast method of incorporating the effects of the stator and/or rotor skew in the torque calculation is introduced. The proposed method requires a minimum number of 2-D finite element evaluations to estimate the electromagnetic torque profile of the skewed machine at a given load condition. This is especially beneficial for rapid evaluation of the effects of stator and/or rotor skew in large-scale design optimization studies. A fast method of evaluating stator tooth forces using a Maxwell stress tensor approach applied to the field quantities calculated using minimum number of 2-D magnetostatic finite element solutions is introduced. Finally, effects of the skew on the developed tooth forces are evaluated.
The conventional scaling rules for the optimal design of electric machines are best suited for na... more The conventional scaling rules for the optimal design of electric machines are best suited for naturally cooled machines with stator winding current densities less than 4A/mm2. In this paper, through a comprehensive sensitivity analysis, first, it is demonstrated that the correlations between some geometric variables and the performance metrics of interior permanent magnet (IPM) motors vary significantly with respect to the stator winding current density. For this purpose, three current densities are selected so as to approximately account for naturally cooled, fan-cooled and liquid-cooled machines. Subsequently, a parameterized IPM motor is optimized at these current densities through a large-scale design optimization algorithm by evaluating a total of 20,000 design candidates. The 100 best designs from each group are then identified and extracted to investigate the scaling rules for the optimal design of such IPM motors with different cooling systems. The outcomes of the study are in correspondence with the conventional design principles for naturally cooled machines. Nevertheless, it is illustrated that these rules vary for fan-cooled and liquid-cooled machines owing to the increased ampere loading, and also heavy saturation of the magnetic core in such machines. A configuration of a 50 hp, 48-slot, 8-pole IPM motor with a single-layer v-type magnet is used as the benchmark of this study.
A novel automated design algorithm for application-based optimization of permanent magnet (PM) ma... more A novel automated design algorithm for application-based optimization of permanent magnet (PM) machines is presented in this paper. The proposed algorithm features precise performance evaluation of the potentially heavily saturated machines at high-energy-throughput operating zones using finite element (FE) techniques. First, the energy consumption function associated with the machine's operating cycle is efficiently modeled by a number of representative load points using a k-means clustering algorithm. Subsequently, a new approach is developed to assess the performance of the machine at each representative load point with proper control to conform to practical operational constraints imposed by voltage and current limits of the motor-drive system. The developed algorithm is applicable to the optimization of any configuration of PM and synchronous reluctance motors over any conceivable operating cycle. Its effectiveness is demonstrated by optimizing the well-established reference/benchmark design represented by the 2004 Toyota Prius IPM motor configuration over a compound operating cycle consisting of common US driving schedules.
This paper describes a systematic method for optimally designing with multiple objectives and dif... more This paper describes a systematic method for optimally designing with multiple objectives and differential evolution (DE) algorithms, current regulated electronically controlled synchronous reluctance (SynRel) machines. A large-scale study with thousands of designs calculated with a ultrafast computationally efficient electromagnetic finite-element analysis (CE-FEA) establishes the performance limitations of conventional radially laminated technology with multiple flux barriers. The potential advantages of employing permanent-magnet (PM)-assisted technology with additional ferrites in the rotor are quantified in terms of substantially improved power factor, specific power, and efficiency. Numerical and experimental results for a 10-hp, 1800-r/min typical rating are included.
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