Academic literature on the topic 'Permanent-magnet synchronous reluctance motors'

Thesis (PhD (Electric and Electronic Engineering))--University of Stellenbosch, 2009.<br>Keywords: position sensorless control, torque control, synchronous machines The work in this thesis deals with energy e cient torque control and rotor position estimation in the full speed range, for a family of synchronous machines that should be used more often in the near future. This family consists of the permanent magnet synchronous machine (PMSM), the reluctance synchronous machine (RSM), the interior-PMSM and the PMassisted- RSM. By designing and controlling these synchronous machines correctly, better performance and higher energy e ciency can be expected compared to the performance and e ciency of an industry standard induction machine. However, applications are limited to variable speed drives (VSD) in a certain power range, e.g. below 100kW. With the growing concern and necessity of a better utilization of energy, it is becoming standard to use electronically controlled power converters between the electricity grid and electrical machines. Therefore, there is a very large scope for the implementation of this synchronous machine technology. For traction applications like electrical vehicles, the optimally controlled synchronous machine technology has a very strong position. Very compact and robust synchronous machines with a very high power density can be designed that may out-perform the induction machine by far. However, one major requirement for most applications is position sensorless control, i.e. rotor position estimation in the whole speed range. To achieve energy e cient torque control, maximum torque per Ampere (MTPA) control should be implemented. It is possible to achieve MTPA control at low speed, but above the rated speed of the machine, eld weakening needs to be performed. The question is how to implement MTPA and e ective eld weakening for any value of speed and DC bus voltage and for any machine within this family of synchronous machines. In this thesis a method is explained to achieve this goal using results from nite element (FE) analysis directly. The scheme may be implemented within a very short period of time. The contribution of this thesis is a general understanding of the problems at hand, with an in-depth view into the mathematical representation of synchronous machines, a generic method of energy e cient torque control and a thorough study of rotor position and speed estimation methods.

In this thesis different methods of optimizing line start permanent magnet motor (LSPM) for magnet cost reduction is studied. Influence of different parameters has been studied by simulating magneto-static and transient FEM models of the machine. Finally a motor design of a LSPM with high rotor saliency has been proposed. The first method investigated is the use of flux barriers in LSPM and its effect on the magnetic flux leakage. The flux barriers reduce the flux leakage and hence help in reducing magnet volume. The second method studied is the use of two different grades of magnets. Using low price magnets help in reducing the total magnet cost without reducing the air gap flux density. The reduction in NdFeB magnet volume is not substantial by using both the methods mentioned above. The third method investigated is increasing the saliency of the rotor by introducing flux barriers and reducing the corresponding magnet volume. Both the magneto static and transient models are used to study the effect of different parameters of the motor. The placement and volume of magnet plays a critical role in motor performance. At first, the developed reluctance torque of the motor is maximized by doing parametric study and then magnets are placed in slots to achieve the required efficiency and power factor. The motor is simulated with NdFeB magnets and with Ferrite magnets. It has been found that using high saliency LSPM motor the NdFeB magnet volume can be reduced significantly. It is also shown that the same performance of motor (as compared to the motor with NdFeB magnets) can be achieved by using Ferrite magnets. The volume of Ferrite magnet required will be larger but still cost-wise using Ferrite is an attractive choice. Therefore, a design of motor is proposed using both NdFeB magnets and Ferrite magnets. Finally, the performance of proposed LSPM motor with high saliency is compared with that of an induction motor.

Recently, permanent magnet assisted (PMa)-synchronous reluctance motors (SynRM) have been considered as a possible alternative motor drive for high performance applications. In order to have an efficient motor drive, performing of three steps in design of the overall drive is not avoidable. These steps are design optimization of the motor, identification of the motor parameter and implementation of an advanced control system to ensure optimum operation. Therefore, this dissertation first deals with the design optimization of the Permanent Magnet Assisted Synchronous Reluctance Motor (PMa-SynRM). Various key points in the rotor design of a low cost PMa-SynRM are introduced and their effects are studied. Finite element approach has been utilized to show the effects of these parameters on the developed average electromagnetic torque and the total d-q inductances. As it can be inferred from the name of the motor, there are some permanent magnets mounted in the rotor core. One of the features considered in the design of this motor is the magnetization of the permanent magnets mounted in the rotor core using the stator windings to reduce the manufacturing cost. At the next step, identification of the motor parameters is discussed. Variation of motor parameters due to temperature and airgap flux has been reported in the literatures. Use of off-line models for estimating the motor parameters is known as a computationally intensive method, especially when the models include the effect of cross saturation. Therefore in practical applications, on-line parameter estimation is favored to achieve a high performance control system. In this dissertation, a simple practical method for parameter estimation of the PMa-SynRM is introduced. Last part of the dissertation presents one advanced control strategy which utilized the introduced parameter estimator. A practical Maximum Torque Per Ampere (MTPA) control scheme along with a simple parameter estimator for PMa-SynRM is introduced. This method is capable of maintaining the MTPA condition and stays robust against the variations of motor parameters. Effectiveness of the motor design procedure and the control strategy is validated by presenting simulation and experimental results of a 1.5 kW prototype PMa-SynRM, designed and manufactured through the introduced design method.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006.<br>This thesis is about the dynamic control of a permanent magnet assisted reluctance synchronous machine (PMA RSM). The PMA RSM in this thesis is a 110 kW traction machine and is ideal for the use in electrical rail vehicles. An application of the dynamic control of the PMA RSM in electrical rail vehicles is to reduce wheel slip. The mathematical model of the PMA RSM is derived and explained in physical terms. Two methods of current control for the PMA RSM are investigated, namely constant field current control (CFCC) and constant current angle control (CCAC). It is shown that CCAC is more appropriate for the PMA RSM. A current controller for the PMA RSM that guarantees stability is derived and given as an analytic formula. This current controller can be used for any method of current control, i.e. CFCC or CCAC. An accurate simulation model for the PMA RSM is obtained using results from finite element analysis (FEA). The accurate model is used in a simulation to verify CCAC. A normal proportional integral speed controller for the PMA RSM is designed and the design is also verified by simulation. Practical implementation of the current and speed controllers is considered along with a general description of the entire drive system. The operation of the resolver (for position measurement) is given in detail. Important safety measures and the design of the electronic circuitry to give protection are shown. Practical results concerning current and speed control are then shown. To improve the dynamic performance of the PMA RSM, a load torque observer with compensation current feedback is investigated. Two observer structures are considered, namely the reduced state observer and the full state observer. The derivation of the full state observer and the detail designs of the observer elements are given. The accurate simulation model of the PMA RSM is used to verify the operation of the observer structures and to evaluate the dynamic performance. Both observer structures are implemented practically and practical results are shown. One method of position sensorless control, namely the high frequency voltage injection method, is discussed in terms of the PMA RSM. This work is additional to the thesis but it is shown, because it raises some interesting questions regarding the dynamic control of the PMA RSM.

This thesis aims to design and develop LSPM motors capable of operating in two distant synchronous speeds with good starting torque and steady state characteristics for variety of industrial applications, in particular offshore and maritime applications. The proposed designs are based on variable pole numbers for the stator and the rotor. The stator winding consist of two independent windings with different pole numbers to switch the winding and change the operating pole count for low and high speed applications. For the motor to operate in these two distinct operating speeds, the rotor must be capable of creating two different magnetic polarities (pole numbers) to adapt itself to the stator operating pole number. For this purpose, two different schemes for the rotor structure are proposed. In scheme I two-speed operation is realized by the combination of electromagnetic torque and reluctance torque which enables the motor to operate as a synchronous PM motor at high speed and synchronous reluctance motor at low speed. In scheme II, rotor with dual PM polarity is proposed which enables the motor to operate as a PM motor at both low and high speed regions.

The electrification of automobiles has emerged as the sustainable powertrain solutionto meet United Nations sustainable development goals of sustainable cities andcommunities, affordable and clean energy, and climate action. The success of theelectrification depends on the efficiency of traction motors. Hence, the automobileindustry is dedicated to improving the performance of electrical traction machinesfor high performance and sustainability. The thesis aims to build various electricalmachine’s concept designs and quantify their behaviour on sustainability andperformance. The thesis objective is to design Permanent Magnet Synchronous Motor (PMSM),Synchronous Reluctance Motor (SynRM), and Permanent Magnet SynchronousReluctance Motor (PM­SynRM). The thesis work comprises of accurate performanceestimation and optimisation of these electrical machines through a finite element based method. The in­house scripts are developed to estimate the performance, electrical losses, and efficiency of these electrical machines through flexible open-source tools. The performance of PMSM with rare-­earth magnet Neodymium Ferrite Boron(NdFeB) and without rare­-earth magnet (ferrite) is done to evaluate the role of bothmagnets in producing torque density. The SynRM is evaluated and optimized usinggenetic algorithms in the thesis. The electrical machines are designed without the useof rare-­earth magnets to eliminate the degradation of the environment and reduce thecost and weight of the motor.<br>The electrification of automobiles has emerged as the sustainable powertrain solutionto meet United Nations sustainable development goals of sustainable cities andcommunities, affordable and clean energy, and climate action. The success of theelectrification depends on the efficiency of traction motors. Hence, the automobileindustry is dedicated to improving the performance of electrical traction machinesfor high performance and sustainability. The thesis aims to build various electricalmachine’s concept designs and quantify their behaviour on sustainability andperformance. The thesis objective is to design Permanent Magnet Synchronous Motor (PMSM),Synchronous Reluctance Motor (SynRM), and Permanent Magnet SynchronousReluctance Motor (PM­SynRM). The thesis work comprises of accurate performanceestimation and optimisation of these electrical machines through a finite element based method. The in­house scripts are developed to estimate the performance, electrical losses, and efficiency of these electrical machines through flexible open-source tools. The performance of PMSM with rare-­earth magnet Neodymium Ferrite Boron(NdFeB) and without rare­-earth magnet (ferrite) is done to evaluate the role of bothmagnets in producing torque density. The SynRM is evaluated and optimized usinggenetic algorithms in the thesis. The electrical machines are designed without the useof rare-­earth magnets to eliminate the degradation of the environment and reduce thecost and weight of the motor.   Sammanfattning på svenska / Abstract in Swedish Elektrifieringen av bilar har framstått som en hållbar drivlinelösning för att mötaFörenade Nationernas hållbara utvecklingsmål för hållbara städer och samhällen, medprisvärda och rena energi och klimatåtgärder. Framgången med elektrifieringen berorpå effektivitet på motorer för framdrivningen. Därför är bilindustrin dedikerad tillatt förbättra prestanda för elmotorer för hållbarhet och hög prestanda. Avhandlingensyftar till att bygga olika konceptdesign för elmotorer för framdrivning och kvantifieraderas beteende på hållbarhet och prestanda. Uppsatsmålet är att utforma Permanent Magnet Synchronous Motor (PMSM),Synchronous Reluktance Motor (SynRM) och permanent magnetassisterad SynRM(PM­SynRM). Examensarbetet består av noggrann prestationsuppskattning ochoptimering av dessa elektriska maskiner genom finit element metod (FEM). Deskripten för att hantera FEM för elektormagnetisk design är in­house utveckladeför att uppskatta flexibelt prestanda, elektriska förluster och effektiviteten hos dessaelektriska maskiner genom att använda öppen källkod. Prestanda för PMSM med en sällsynta jordartsmagnet (NdFeB) och PMSM utansällsynta jordartsmagnet (ferrit) räknades fram för att utvärdera båda magneternasroll för att producera vridmomentdensitet. SynRM och PM­SynRM maskinernautvärderas och optimeras med hjälp av genetiska algoritmer i avhandlingen.De studerade elektriska maskinerna är designad utan användning av sällsyntajordartsmagneter för att eliminera miljöförstöring och minska motorns kostnad ochvikt.