Table of contents monday, September 9, 1: 30pm-4: 00pm modular Multi-Level Converters, hvdc, and dc grids I 3
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- Bu səhifədəki naviqasiya:
- Materials and Manufacturing Issues of Electric Machines
- Induction Motor Drives
- PM and IPM Motor Drives I
| 8:55AM Magnetic Field Analytical Computation in Synchronous Reluctance Machines Considering the Iron Saturation [#634]
Hanafy Mahmoud, Nicola Chiodetto and Nicola Bianchi, Padova University, Italy This paper deals with an analytical model of REL motor considering the stator slotting effect and the magnetic saturation in the stator and rotor iron paths. It joints the field distribution at the air-gap to a lumped-parameter magnetic network. As an example, 36-slot 4-pole machine is analyzed, considering three flux barriers per pole. Finite element analysis confirms the results achieved by means of the analytical model. 9:20AM Performance Comparison of Short Pitched and Full Pitched Switched Reluctance Machines for Off-Road Vehicle Applications [#1526]
This paper presents a comprehensive comparison of switched reluctance machines (SRM) with short pitched and full pitched windings for the same machine geometry. A switched reluctance machine designed for off-road vehicles with short-pitched windings is rewound with full-pitched windings and the two winding structures are compared. The effect of number of turns on the torque speed characteristics is also investigated. The two different winding configurations were evaluated with unipolar excitation at the same bus voltage level of the driver. The machines are compared with respect to their electromagnetic behavior, operating range, torque per ampere, and efficiency. The comparison would better guide designers on what type of configuration would best suit to their applications. The comparison is conducted with the aid of Finite element analysis. An experimental 50 kW prototype for the off-road vehicle application is used for experimental validation. 9:45AM A Fault Tolerant Machine Drive based on Permanent Magnet Assisted Synchronous Reluctance Machine [#1563]
A fault tolerant machine drive based on permanent magnet (PM) assisted synchronous reluctance machine is proposed and investigated for safety critical applications. In order to achieve enhanced fault tolerant capability, the risk of the permanent magnet field that cannot be turned off under fault conditions is minimized without compromising the torque density and efficiency. This is achieved by employing a synchronous reluctance rotor topology with embedded permanent magnets. Three independent 3-phase windings are adopted and a segregated winding configuration is devised to ensure non-overlapping in the three 3-phase winding sets. Each 3-phase winding set is driven by a standard 3-phase inverter, which facilitates fast integration and cost reduction. The performance under various fault conditions has been evaluated by FE simulations. The results show that the proposed machine drive exhibits high performance as well as excellent fault tolerant capability under various faults, including open circuit, terminal short circuit, and inter-turn short circuit, etc. 10:10AM A General Approach for the Analysis and Comparison of Hybrid Synchronous Machines With Single-Axis or Bi-Axial Excitation [#1674]
Hybrid Excitation Synchronous Machines allow broad flux regulation, and therefore a very wide Constant Power Speed Range. Literature shows that it is possible to build them both with a Single Axis and with a Bi Axial excitation. This paper presents a unified approach for the analysis, comparison and performance prediction of the two structures. Finite element simulation and experimental tests are carried out on a Torus type Axial Flux prototype, which, having two rotors, one equipped with PM and one with WE, allows for an easy structure reconfiguration on the same machine. 10:35AM Flux Modulation Principles of DC-Biased Sinusoidal Current Vernier Reluctance Machines [#728]
DC-biased sinusoidal current vernier reluctance machines (DC-biased-VRMs) are with a doubly salient structure, and their phase currents contain an alternating current (AC) component and a direct current (DC) component. Hence, their main features are one set of concentrated windings compared with variable flux reluctance machines (VFRMs), low vibration and noise due to smooth current, compared with switched reluctance machines (SRMs), and robust rotor structure. Besides, its achievable high slot fill factor can improve the torque density further. However, the existing DC- biased VRMs, whose stator/rotor slots of 6/4 and 6/8 have high torque ripple. In this paper, based on the flux modulation principles, the torque production mechanism of DC-biased VRMs are analyzed and two slot combinations of 12/8 and 12/10 are proposed. Firstly, the machine topology and inverter main circuit is illustrated. Secondly, the stator armature pole pairs/rotor pole relationship and pole ratio is given. Furthermore, the inductance, optimal current configuration for maximum torque and lowest torque ripple are theoretically analyzed and by the finite element analysis (FEA). Finally, one prototype has been designed and under built, and the experimental results will be then given. Materials and Manufacturing Issues of Electric Machines Tuesday, September 20, 8:30AM-11:00AM, Room: 101A, Chair: Aldo Boglietti, Daniel Ludois 8:30AM Stator Lamination Geometry Influence on the Building Factor of Synchronous Reluctance Motor Cores [#665] Andrea Cavagnino and Zbigniew Gmyrek, Politecnico di Torino, Italy; Lodz University of Technology, Poland The study investigates the influence of the lamination geometry on the building factor of stator magnetic cores, quantifying by experiments the influence of the punching and the annealing process. The research and the experimental activity are focused on small fractional power synchronous reluctance motors, where the punching process effect is expected to be very impacting, not only for the stator iron losses increase, but also because the current magnetizing component is dominant in the total adsorbed current. However, the obtained results are particularly interesting for any fractional and low power electric machines, whose cores are built with punched or laser-cut laminations. 8:55AM Influence of PM Coating on PM Magnetization State Estimation Methods Based on Magnetoresistance Effect [#1589]
Variable flux PMSMs (VF-PMSMs) are gaining importance, especially in automotive applications. The use of such machines will require the development of methods to estimate the permanent magnet (PM) magnetization state. PM magnetization state estimation methods reported in literature include BEMF and high frequency signal injection. One advantage of high frequency signal injection methods is that they can operate over the whole speed range, with practically no interference with the regular operation of the machine. Magnetization estimation using high frequency injection relies on the variation of the d-axis high frequency inductance with the saturation produced by the magnets. Alternatively, the changes of the magnet electrical resistance due to the magnetoresistive effect can also be used for this purpose. These methods have been tested with different materials, including NdFeB, AlNiCo and SmCo magnets. NdFeB magnets are usually protected from oxidation using NiCuNi coating. However, NiCuNi also shows magnetoresistance effect, and can affect therefore the performance of the method when used with magnets having NiCuNi coating. This paper studies the effects of PM coating on the performance magnetization estate estimation by means of high frequency signal using the magnetoresistance effect. The analysis will include NdFeB, AlNiCo and SmCo magnets. 1 9:20AM Investigation of the Impact of Production Processes on Iron Losses of Laminated Stator Cores for Electric Machines [#341]
To further improve the power density of modern electric drive technologies many motor designers decide to increase the rotational speed of the motor up to several tens of thousands revolutions per minute. Along with these high frequencies of the fundamental wave of the flux density inside the laminated stator cores, the electromagnetic strain of the core and the importance of the iron losses are increasing. Due to this, the high amount of different mechanisms, responsible for these iron losses, need to be identified and associated to the appropriate production process. For this reason, a suitable and inline-capable electromagnetic measuring method is used to determine the iron losses for real motor stator core geometries and to separate the impact of different production steps. In this paper, the large number of manufacturing methods for stator cores is presented and the iron losses are assigned to the corresponding production step in an overall consideration. The cause of the measured losses are identified and described. The mentioned measuring adapter can also be used to monitor a specific assembly line with regard to separation and joining quality to represent an innovative and economic possibility of quality assurance. 9:45AM Influence of Manufacturing Tolerances on Cogging Torque in Interior Permanent Magnet Machines with Eccentric and Sinusoidal Rotor Contours [#64]
The rotor shaping methods are frequently used to reduce the cogging torque in interior permanent magnet (IPM) machines. This paper investigates the influence of manufacturing tolerances on cogging torque in IPM machines with eccentric and sinusoidal rotor contours. First, two 12-slot/8-pole IPM machine models are established and the fundamental performance under ideal conditions is presented. Then, based on the most sensitive distributions of non-ideal PMs and assembly tooth-bulges, additional cogging torque components are calculated respectively, together with a comparative study to identify the different sensitivities between the two rotor contour designs. For verification, the field spatial harmonics with and without considering the tolerances are further analyzed, followed by tests on the prototypes with and without amplified tolerances. 10:10AM A Practical Approach of Electromagnetic Analysis with the Effect of the Residual Strain due to Manufacturing Processes [#1383]
Toward reliable and advanced machine designs, a practical modeling method of degraded steel sheets due to manufacturing processes is proposed. The advantage of the proposed method is the fact that the required material data can be measured with the standard single sheet testing without special measurement equipment so that machine manufactures will be able to take into account of the degradation effects according to their manufacturing processes. In the proposed approach, an approximation function which represents spatial variation of the degradation for each BH and loss property is identified using measurement data of steel sheet strips which have different widths. The identified approximation functions provide the material properties for Finite Element Analysis. It is shown that FEA calculations using the proposed method reproduce well the measurement results of cut steel sheets.Obtained degradation function is also applied to a PMSM. We investigate how the degradation function influences on the performance of the machine such as the back EMF. 10:35AM Investigation of Emerging Magnetic Materials for Application in Axial-Flux PM Machines [#539]
This paper investigates the performance of three magnetic materials: silicon iron, soft magnetic composite and amorphous magnetic material, as the stator of an axial-flux permanent-magnet machine. Three stators, one of each material, are built and tested with the same rotor. The losses of each of the machines are separated using a combination of 3D finite-element analysis and experimental testing under open-circuit and loaded conditions. Induction Motor Drives Tuesday, September 20, 8:30AM-11:00AM, Room: 101B, Chair: Sertac Bayhan, Di Pan 8:30AM A Compact Active Filter to Eliminate Common-Mode Voltage in a SiC-based Motor Drive [#1155] Kellan Euerle, Kartik Iyer, Eric Severson, Rohit Baranwal, Saurabh Tewari and Ned Mohan, University of Minnesota, United States; MTS Systems Corporation, United States This paper presents an active compensation device for common-mode (CM) voltage elimination in 3-phase space-vector pulse-width-modulated (SVPWM) inverters. The proposed device consists of a single-phase 2-level inverter (H-bridge) which supplies a compensating voltage to the inverter via a step- up common-mode transformer tied to all three phases at the output. The H- bridge active filter is supplied by a low voltage bus and switched several orders of magnitude faster than the inverter switching frequency. This device takes advantage of the direct knowledge of the switching pulses sent to the inverter to predict and generate the compensating voltage. A technique is employed to subtract the low frequency harmonics from the modulation of the H-bridge which allows for the size of the common-mode transformer to be reduced significantly. Small passive components are added to attenuate the active filter's PWM frequency content and thus produce an effective compensating voltage. This paper will review existing common-mode voltage compensation techniques and demonstrate that the proposed method is a logical choice for certain drive applications. Design considerations are included to provide understanding and guidance for implementation of the device, as well as MATLAB/Simulink simulation results to demonstrate the operation of the active compensation device. Final validation is presented through experimental results from a hardware prototype. 8:55AM Stator Inter-Turn Fault Detection for Seamless Fault-Tolerant Operation of Five-Phase Induction Motors [#1201]
Multiphase motors have been shown to be advantageous in safety-critical and cost sensitive applications due to their ability to operate with open phases. However, for true fault-tolerant operation the motor drive must be able to detect an incipient fault and then transition to post fault operation. It is also desirable for the fault detection method to be non-intrusive and require minimal additional sensing. This paper investigates a low cost diagnostic method using DC voltage injection for monitoring and detection of stator inter-turn faults in five-phase induction motors. The proposed method is incorporated into the control loop and allows the motor to seamlessly transition from healthy to fault-tolerant operation after the fault is detected, with minimal modification to the control logic. It is validated with simulations as well as implemented on a microcontroller and tested on a five-phase induction motor with winding taps to emulate the inter-turn fault condition. 9:20AM Rotor Temperature Estimation in Doubly-Fed Induction Machines Using Rotating High Frequency Signal Injection [#474]
Thermal monitoring is a common feature in most of electric machine drives since thermal overloading is one of the most common causes of motor failures. Contact-type sensors are normally used to measure the stator temperature in electric machines. However, use of this type of sensor is not advisable in the rotor as it requires cabling to a rotating part or the use of a wireless transmission system. Consequently, measurement of the rotor temperature is not easy in practice and is not normally implemented in standard machines. An alternative to rotor temperature measurement is rotor temperature estimation. Up to date, only thermal models have been used for rotor temperature estimation in doubly-fed induction machines (DFIMs). This paper proposes rotor temperature estimation in DFIMs using high-frequency signal injection. The proposed method estimates the rotor temperature from the rotor high frequency resistance, which us a function of the rotor windings temperature. The method does not interfere with the normal operation of the drive and can be implemented in existing DFIM drives without requiring additional hardware 9:45AM Maximum Torque Output for Volts/Hz Controlled Induction Machines in Flux-weakening Region [#953]
For maximum torque control of induction machines (IM) in flux-weakening region, the following problems exist: 1. In Volts/Hz scalar control mode, a slow frequency ramp time cannot provide sufficient electromagnetic torque, whereas the excessive acceleration leads to overcurrent shutdown and system collapse; 2. In vector control mode, the under-estimated leakage inductance in field- weakening region can lead to system instability. To solve these problems, this paper presents a method based on both stability criteria and maximum torque capability for determining a proper frequency ramp-up profile. It retains the maximum torque output capacity on the basis of guaranteeing system stability in flux-weakening region. A proportional and integral (PI) controller is employed to adjust the frequency ramp time, which will be halted if the magnetizing current exceeds a predefined limit. Moreover, the proposed scheme has a larger tolerance of underestimated leakage inductance as compared with the vector controlled IM drives in flux-weakening region. Simulation studies on a 3hp (2.2kW) and a 20hp (15kW) have been conducted in both Volts/Hz and vector control modes. Experimental validation is presented on a 3hp (2.2kW) platform in Volts/Hz control mode. Both simulation and experimental results validate the analysis and show effectiveness of the proposed method in the defined scenarios. 10:10AM Performance Investigation of Selected Prediction Vectors Based FS-PTC for 3L-NPC Inverter Fed Motor Drive [#28]
Computational burden is a major hurdle for practical implementation of finite- state predictive torque control (FS-PTC) of motor drive fed by a multi-level inverter. One of the reasons of computational complexity is that all voltage vectors are evaluated for prediction and actuation. This paper proposes selected number of voltage vectors for the prediction and actuation, which are called prediction vectors in FS-PTC, and the performance is investigated for a three-level neutral-point clamped (3L-NPC) inverter fed motor drive. The number of prediction vectors is reduced based on the position of stator flux and the deviation in stator flux from its reference. Experimental results confirm that the computational burden is reduced significantly, while the dynamic performance in terms of torque and flux ripple, stator current total harmonic distortion (THD), neutral-point voltage, torque rise time, and average switching frequency is comparable to the all voltage vectors based FS- PTC. 10:35AM Inverter-fed Drive Stator Insulation Monitoring based on Reflection Phenomena Stimulated by Voltage Step Excitation [#895]
Reflected wave transient phenomena in voltages and currents of inverter-fed drives caused by voltage source inverters (VSI) operating with pulse width modulation (PWM) with high dv/dt rates are well known and analyzed in many studies. The reflection phenomena occurring at the machine terminals, resulting in high overvoltages are one reason for the stress and aging mechanism of AC machines insulation system. The motivation of this work arises out of the need for a continuous monitoring of the insulation health state for traction drives systems in order to ensure high reliability of the drive over many years of operation. With a voltage step initiated by a switching transition, the inverter elicits a response in the drive system. By using the information of the resulting transient effects, conclusions can be drawn on basis of the oscillation behavior which are indicative for a change in the insulation system. Investigations in this work show that an alteration in the shape of the system transients, in peak values as well as frequency components, correlates with a dielectric insulation capability of the machine winding insulation. Measurements on a small, low voltage, random wound, induction machine (5.5kW) and a medium voltage induction machine (1.4MW) with formwound coil based stator system are performed. Artificially induced insulation aging is realized by accelerated thermal aging to demonstrate the effect. Additionally, two different inverter types are used, with standard IGBT modules (dv/dt 2-4kV/us) and new SiC semiconductor inverter technology (dv/dt up to 20kV/us), to analyze the influence of the shape of the excitation voltage step. PM and IPM Motor Drives I Tuesday, September 20, 8:30AM-11:00AM, Room: 101CD, Chair: Nicola Bianchi, Prerit Pramod 8:30AM maximum torque per ampere control in stator flux linkage synchronous frame for DTC-based PMSM drives without using q-axis inductance [#286] Atsushi Shinohara, Yukinori Inoue, Shigeo Morimoto and Masayuki Sanada, Osaka Prefecture University, Japan When direct torque control (DTC) is applied to permanent magnet synchronous motor (PMSM) drives, the relationship between the torque and stator flux linkage is important for high-efficiency drives because DTC requires them as references. In the stator flux linkage synchronous frame (M-T frame), the torque is described by a simple equation using the T-axis current. However, the M-axis current is neglected in the equation. This paper derives the relationship between the M-axis current and the stator flux linkage and proposes a maximum torque per ampere (MTPA) control strategy for direct torque controlled PMSM drives using the above relationship. The proposed method does not require the q-axis inductance, which often varies due to the magnetic saturation. The simulation and experimental results verify that the MTPA condition can be obtained with the proposed method. 8:55AM A Novel Direct Torque Control Strategy for Interior Permanent Magnet Synchronous Motors Driven by a Three-level Simplified Neutral Point Clamped Inverter [#290]
Compared to the three-level neutral point clamped (3L-NPC) inverter, its simplified version, the 3L-SNPC, uses fewer switching devices to achieve a multi-level output. However, it offers fewer voltage vector selections, limiting its usefulness for motor drive applications. This issue is overcome through a proposed direct torque control (DTC) strategy utilizing the concept of virtual voltage vectors to increase the number of voltage vector selections available. In addition, a DTC based switching table employing at least one voltage vector within each sampling period is proposed to reduce the torque ripple. Further, the issue of neutral point capacitor voltage unbalance is addressed. The strategy is modelled for an Interior Permanent Magnet Synchronous Motor driven by a 3L-SNPC, and simulation results prove its feasibility. To the knowledge of the authors, the proposed strategy has not previously been reported.
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