Table of contents monday, September 9, 1: 30pm-4: 00pm modular Multi-Level Converters, hvdc, and dc grids I 3
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- Poster Session: Power Semiconductor Devices, Passive Components, Packaging, Integration, and Materials
| P4903 Effects of External Field Orientation on Permanent Magnet Demagnetization [#1648]
Peng Peng, Han Xiong, Julia Zhang, Wanfeng Li, Franco Leonardi, Michael Degner, Chuanbing Rong, Feng Liang and Leyi Zhu, Oregon State University, United States; Ford Motor Company, United States This paper investigates how the orientation of the applied demagnetizing magnetomotive force (MMF) affects the demagnetization behavior of Nd-Fe-B magnets that are widely used for permanent magnet synchronous machines (PMSMs). This work designs and builds a customized test fixture that can produce a magnetic field with varying orientation and intensity to demagnetize magnet samples. A computer-controlled 2D mapping device is used to record the flux density above the test samples. The measurement results are compared with the 3D finite element analysis (FEA) simulations. The understanding and insight obtained from this work will help the robust design of magnets for high power density PMSMs with improved capability of withstanding demagnetization during overcurrent faults. P4904 Analytical Approach for Determining Inductance Matrix, Harmonic Voltage and Torque Ripple of Slotted PM Motors [#919]
This paper proposes a novel approach for calculating position-dependent inductance matrix of slotted permanent magnet synchronous motors (PMSMs) and advanced analytical models for machine voltage and torque. In a real PM machine, the slotted structure of the stator and rotor causes unintended variations in air-gap permeance and magneto- motive force (MMF). The proposed approach analyzes the effects of these variations on air-gap flux and winding inductances. The calculated d-q inductance matrix contains harmonic and coupling components. In this paper, both voltage and torque models are modified to reflect the changes in inductance matrix. Some nonlinear terms due to structural saliency are additionally considered. The results of simulation with finite-element method (FEM) are presented to verify the validity of the proposed inductance, voltage and torque models. P4905 Cogging Torque Minimization in Transverse Flux Machines [#1312]
This paper presents the design considerations in cogging torque minimization in two types of transverse flux machines. The machines have a double stator-single rotor configuration with flux concentrating ferrite magnets. One of the machines has pole windings across each leg of an E-Core stator. Another machine has quasi-U-shaped stator cores and a ring winding. The flux in the stator back iron is transverse in both machines. Different methods of cogging torque minimization are investigated. Key methods of cogging torque minimization are identified and used as design variables for optimization using a design of experiments (DOE) based on the Taguchi method. A three-level DOE is performed to reach an optimum solution with minimum simulations. Finite element analysis is used to study the different effects. Two prototypes are being fabricated for experimental verification. P4906 Torque Ripple Reduction in a Flux-Switching Permanent Magnet Machine Targeted at Elevator Door Applications by Minimizing Space Harmonics [#1344]
A flux-switching permanent magnet (FSPM) machine using ferrite magnet is proposed to replace the permanent magnet synchronous motors (PMSMs) in elevator doors. In order to improve both mechanical robustness and manufacturability, bridges around permanent magnet (PM) slots have been adopted in the C-shaped core of an FSPM machine. The optimization of the C-shaped stator is conducted, and its prototype has been built up for experimental validation. Back- electromotive force (EMF) is estimated to prove that simulated results are correct and reliable. Compared to a PMSM designed for elevator doors, the efficiency of an FSPM machine is significantly improved in spite of using ferrite PM that is utilized in the PMSM, but there is a disadvantage in torque ripple due to the interaction of harmonic components between back-EMF and magneto-motive force (MMF). However, most of researches on an FSPM machine have been focused on eliminating harmonic components of back-EMF. In this paper, the design process of an FSPM machine based on winding function theory will be given to diminish torque ripple by considering the harmonics of back-EMF and MMF in air gap. P4907 On Saliency Enhancement of Salient Pole Wound Field Synchronous Machines [#1378]
Salient pole wound field synchronous machines (WFSMs) share similar torque characteristics as permanent magnet (PM) machines, but are free of permanent magnet material since a wound rotor winding instead generates the required field flux. In addition to cost advantages, the rotor field flux is readily varied making these machines attractive for traction and generator applications. This paper introduces flux barrier structure on rotor design to improve the saliency and thus the torque production of a conventional synchronous machine. Analysis are done using both dq- equivalent circuit model and finite element (FE) calculations. Flux barrier width is carefully tuned in FE analysis. Comparison is made to a conventional salient pole structure whereby a steady state torque improvement is achieved at rated to high stator current, and total loss is reduced in field weakening region. P4908 Fast and Accurate Analytical Calculation of the Unsaturated Phase Inductance Profile of 6/4 Switched Reluctance Machines [#847]
Accurate calculation of the phase inductance profile of switched reluctance machines (SRMs) is of crucial importance in SRM design because it is a key parameter to predict the performance indices such as the torque and core loss. Instead of using the time-consuming finite element analysis (FEA) or the methods that require prior knowledge of magnetic fields from an FEA such as curve fitting and magnetic equivalent circuit (MEC), this paper proposes a fast and accurate analytical approach to determine the unsaturated phase inductance of an SRM at arbitrary rotor positions by solving the partial differential equations of magnetic scalar or vector potentials based on Maxwell equations. Conformal mapping is applied to deal with the non-radial or non-tangential geometric structures when calculating the inductance of the SRM. The agreement between the results of the proposed analytical method and FEA validates the analysis. P4909 An Analytical Approach for Determining Harmonic Cusps and Torque Dips in Line Start Synchronous Reluctance Motors [#1330]
Excellence of line start synchronous reluctance motors (LS-SynRM) such as their high efficiency amongst other types of line start motors necessitates the existence of analytical methods in their design. The start-up period of these motors is of high importance and regarding this, the cage design needs to be discussed thoroughly since the squirrel cage is responsible for speeding up the motor to reach at synchronism. One of the issues in this sense is the rich harmonic content of the air-gap MMF arising from irregular bars configuration which afterwards could lead to creation of the torque dips in the torque-speed characteristic of the machine and making it incapable of synchronization under load. An analytical approach to calculate these harmonic effects while also considering the reluctance rotor contribution on them is proposed in this paper. This scheme starts from the stator winding configuration as a known parameter, obtaining the air gap MMF due to only the stator magnetic field, calculating the current and voltages induced through the rotor bars considering the effect of saliency using the model proposed in [1, 2]. Next, harmonic contribution of the rotor cage in the air gap MMF is derived. Finally, probable harmonic cusps and consequently torque dips is found in the torque-speed characteristic of the motor which is helpful in anticipating the synchronization capability under various loads. The results have been verified with a sample 4-pole, two flux barriers per pole LS-SynRM which suffers crawling due to the existence of the torque dips in its torque-speed characteristic. All simulations have been done by finite element analysis (FEA) software and a comprehensive program was written in Matlab to implement the proposed algorithm. P4910 Multi-Objective Design and Optimization of Generalized Switched Reluctance Machines with Particle Swarm Intelligence [#1421]
This paper proposes a fast and generalized multi-objective design and optimization method for the Switched Reluctance Machines (SRM). An analytical design model for SRMs with any feasible stator and rotor slot combinations is firstly developed, which can accurately evaluate a SRM design much faster than the prevalent finite element analysis (FEA) method. In addition, a novel method for multi-objective optimization of SRM is proposed based on this analytical model, and the number of prime variables to be optimized is reduced to only five. A canonical Particle Swarm Optimization (PSO) algorithm with penalty function is applied to find the optimal solution for a user defined objective function. After several rounds of searching process with the PSO, the optimal regions can be found for the design variables in terms of the performance indices (PIs). Finally, the optimized designs are validated by FEA. This method can generate the optimized SRM designs subject to different design requirements and accelerate the entire optimization process. P4911 Design and Comparison of Concentrated and Distributed Winding Synchronous Reluctance Machines [#1536]
This paper presents the design and comparison of two types of synchronous reluctance machines. The compared machines differ in their respective type of winding: One is equipped with a conventional full pitch distributed winding while the other one imparts an integer slot concentrated winding. Challenges for the application of concentrated windings to synchronous reluctance machines are examined. The tradeoff concerning a winding configuration with high winding factor and low space harmonic content is carved out. For the concentrated winding machine a winding configuration which is prioritizing a low space harmonic content over a high winding factor is chosen. Both machines were designed for equivalent performance requirements and design space. Finally, several calculations were done and the individual assets and drawbacks are opposed. P4912 Reduction in Torque and Suspension Force Ripples of an Axial-Gap Single-Drive Bearingless Motor [#131]
This paper investigates reduction in torque and suspension force ripples of an axial-gap type bearingless motor with one-degree-of-freedom (DOF) active positioning in the axial direction. This one-DOF controlled bearingless motor employs only one set of three-phase winding and one three-phase inverter, called a single-drive bearingless motor (SDBelM). The proposed axial-gap SDBelM combines a repulsive permanent magnetic coupling that stabilizes four- DOF radial and tilting motions. The suspension force and torque, which are regulated by the d- and q-axis currents, respectively, are theoretically derived considering the spatial harmonics of the flux density distribution induced from the permanent magnets. For reduction in torque and force ripples, we have proposed the improved magnet shape with the gap between the magnet pieces. The finite element method calculation shows that the proposed PM configuration is effective to reduce the torque and the suspension force ripples. P4913 Advancements in High Power High Frequency Transformer Design for Resonant Converter Circuits [#970]
Medium and high frequency converters are gaining increasing interest for high power applications such as renewable energy and dc grids. Medium and high frequency transformers are an essential component in such converters. Advancing resonant converters to higher power levels challenges the transformer design in multiple aspects including power levels, switching frequency, ac and dc voltages insulation requirements and parasitic parameters. This paper presents design methods and recommendations for transformers that accomplish an industry- leading combination of power levels in the MW-class resonant frequencies up to 20kHz, operating AC voltages up to 5 kV, and dc offset voltages up to 300 kV. Design examples and test results of prototypes are presented along with results from applications where the transformers are integrated within high frequency converters. P4914 Active Damping of Ultra-fast Mechanical Switches for Hybrid AC and DC Circuit Breakers [#1026]
An active damping method for Thomson coil actuated ultra-fast mechanical switches is proposed, including its control. Ultra fast mechanical switches are crucial for both DC and AC circuit breakers that require fast-acting, current-limiting capabilities. However, fast motion means high velocity at the end of travel, resulting in over-travel, bounce, fatigue, and other undesirable effects. The active damping proposed in this paper not only avoids such issues, but actually enables faster travel by removing limitations that would otherwise be necessary. This active damping mechanism is applicable in particular to medium and high voltage circuit breakers, but can be extended to actuators in general. A 15kV/630A/1ms mechanical switch, designed to enable the fast protection of medium voltage DC circuits, is used as a test-bed for the concept. It is based on the principle of repulsion forces (Thomson coil actuator). By energizing a second coil, higher opening speeds can be damped with limited over-travel range of the movable contact. The overall structure is simple, and the size of the overall switch is minimized. To validate the concept and to study the timing control for best active damping performance, both finite element modeling and experimental studies have been carried out. P4915 A Diagnosis Procedure in Standalone Mode for Inter Turn Short Circuit Fault of PMSMs through Modified Self-Commissioning [#846]
In this paper, an comprehensive impedance analysis is proposed to detect inter turn short circuit fault in PMSMs at start-up. This method requires a very small computational load (less than 5% CPU bandwidth) and is easy to implement. The procedure is performed at start-up during standstill mode, and hence agnostic to well-known issues caused by transients, load/speed level or controller coefficient dependency. In order to distinguish the inter turn shorts from the eccentricity fault which exhibits similar behaviors, a classification algorithm is introduced based on stator resistor and inductances. Moreover, the effect of stator iron core saturation on the electric parameters analyzed in depth. Both 2-D FEA simulation and experimental test results are provided to show the efficacy of this method. P4916 Improved Condition Monitoring of the Faulty Blower Wheel Driven by Brushless DC Motor in Air Handler Unit (AHU) [#1185]
The AHU (air handler unit) is one of the main research objects in HVAC (heating, ventilating and air conditioning) system containing coils, blower wheel, heater, etc. Most of the high efficiency blower wheels are driven by BLDC (brushless DC) motor. This paper mainly focuses on two severe problems in blower wheel, namely airflow blockage and unbalanced load of fan motor. Early diagnosis of these problems decreases energy consumption in HVAC system significantly. Condition monitoring method applied to both the stator current and stray flux is utilized in unbalanced load condition in a BLDC motor. The fundamental frequency and second harmonics of stray flux are analyzed as indicators under unbalance load condition. The discrimination between airflow blockage and unbalanced load based on stator spectrum analysis is also discussed in this paper. Some experiment results are given to prove that this method provides more efficacy and stability to diagnose the faults in blower wheel. P4917 Mitigation Method of the Shaft Voltage according to parasitic capacitances of the PMSM [#1219]
In this study, we propose the mitigation method of a shaft voltage according to change in parasitic capacitances of a permanent magnet synchronous motor (PMSM). First, we designed the equivalent circuit taking into account all parasitic capacitances. Then, we deducted that rotor-to-winding and stator-to- rotor capacitances mainly affect the shaft voltage. The stator-to-rotor capacitance depends on the air-gap length, which directly affects output torque characteristics of the motor. In case of the rotor-to-winding capacitance, it depends on the distance from the rotor to winding, which have effects on torque ripple, but it does not affect average torque of the motor. Thus, rotor-to- winding capacitance is determined as a variable for mitigation of the shaft voltage. According to change in the rotor-to-winding capacitance, we obtained and compared the results of the shaft voltage, average torque, and torque ripple. P4918 3-D Equivalent Magnetic Circuit Network for Precise and Fast Analysis of PM-assisted Claw-Pole Synchronous Motor [#288]
PM-assisted claw-pole synchronous motor (CPSM) has commonly been used in a variety of industrial applications, thanks to its robust structure and high energy density. However, such motor has an axially asymmetric rotor configuration, which induces the corresponding 3-D magnetic field distribution. Thus, this paper develops an infinitesimal hexahedron-element-based 3-D equivalent magnetic circuit network (EMCN) to estimate the performance of the PM-assisted CPSM. The hexahedron element can be considered as an optimum unit element in describing the configuration of the PM-assisted CPSM in detail. That eventually makes it possible to analyze the specific 3-D magnetic field distribution from which the flux-linkage, the back-electro motive force, the d- and q-axis inductances, and the electromagnetic torque are also being calculated. The results from the 3-D EMCN are compared with those from the 3-D FEA and/or the experiment so as to validate the accuracy. Finally, it is proved that the 3-D EMCN requires a shorter computing time than the 3-D FEA. P4919 Superconducting and Conventional Electromagnetic Launch System for Civil Aircraft Assisted Take-off [#471]
This paper compares three possible linear motor topologies for an electromagnetic launch system to assist civil aircraft take-off. Assisted launch of civil aircraft has the potential of reducing the required runway length, reducing noise and emissions near airports and improving overall aircraft efficiency through reducing engine thrust requirements. A comparison is made of practical designs of a linear induction motor, a linear permanent magnet synchronous motor and a superconducting linear synchronous motor to propel the A320-200 aircraft. The machine design requirements are established considering aerodynamic and engine performance and allow the aircraft to safely complete the take-off procedure. Analytical design of conventional synchronous and asynchronous linear motor will be compared with finite element analysis. A superconducting synchronous motor design is also considered, accounting for full system losses including the cryocooler power requirement and the mechanical and design constraints necessary for the cooler and the superconducting coils. P4920 Design of Integrated Radial and Dual Axial-Flux Ferrite Magnet Synchronous Machine [#537]
Recently, significant attention has been paid to the use of ferrite magnets in the main traction machines of electric vehicles/hybrid electric vehicles (EVs/HEVs). However, while ferrite magnets are advantageous in terms of cost, they provide poor magnetic performance in comparison to the neodymium (NdFeB) magnets used in high-performance, high-efficiency machines with high torque densities. To overcome this issue, the application of axial-flux structures (AFSs) to ferrite magnets has been proposed, and it is anticipated that the extended air gap area created when an AFS is used could compensate for their poor magnetic properties. As an additional countermeasure, we propose an integrated radial and dual axial-flux (IRDAF) structure that has one radial-flux gap and two axial-flux gaps. Evaluations performed using finite element analysis show that a machine designed with our proposed IRDAF structure would provide good performance in terms of output torque, efficiency, and irreversible demagnetization. Poster Session: Power Semiconductor Devices, Passive Components, Packaging, Integration, and Materials Tuesday, September 20, 3:00PM-4:30PM, Room: Exhibit Hall, Chair: Giovanna Oriti, Enrico Santi P5101 Comprehensive Evaluation of a Silicon-WBG Hybrid Switch [#1423] Amol Deshpande and Fang Luo, The Ohio State University, United States; the Ohio State University, United States In this paper, a hybrid switch (HyS) consisting of a large silicon (Si) IGBT die in parallel with a small wide bandgap (WBG) die is proposed for generic power conversion drives. This HyS produces an inherent better conduction performance compared to the Si IGBT and WBG. A gate control option is recommended for minimum switching losses and switching frequency as high as 78 kHz can be achieved in HyS based converters. A parametric study was performed on the influence of the parasitic interconnect inductances within the switch. The recommended gate control option can be used for an inductance unbalance of less than 10 nH within the IGBT and WBG cell. For higher inductance an alternative gate control strategy is proposed for reduced switching losses. Experimental results show the benefits of the HyS. An algorithm is proposed for the optimum Si/WBG die current ratio. A case study involving transient thermal analysis is performed to show that a Si/WBG current ratio as high as 6:1 can be realized while ensuring the integrity of both dies.
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