Performance comparison between Surface Mounted and Interior PM motor drives for Electric Vehicle application

Electric Vehicles make use of permanent magnet synchronous traction motors for their high torque density and efficiency. A comparison between interior permanent magnet (IPM) and surface mounted permanent magnet (SPM) motors is carried out, in terms of performance at given inverter ratings. The results of the analysis, based on a simplified analytical model and confirmed by FE analysis, show that the two motors have similar rated power but that the SPM motor has barely no overload capability, independently of the available inverter current. Moreover the loss behavior of the two motors is rather different in the various operating ranges with the SPM one better at low speed due to short end connections but penalized at high speed by the need of a significant de-excitation current. The analysis is validated through finite-element simulation of two actual motor design

Design of Powder Core Motors

The goal of the study presented in this thesis is to evaluate the advantages and drawbacks of using powder technology in the design of the iron core of small claw-pole electric motors. The use of soft magnetic composites (SMC) and compaction technology allows the creation of complex 3D iron cores. The additional dimension opens for new solutions of the electromechanical energy conversion. A claw-pole motor among the transversal flux machines that has particularly high specific torque is in the focus of research interest. Generally, as the iron core can be more complicated, the winding is chosen to be simpler in the powder core motors. The thesis focuses on the machine design of a single-phase and a two-phase low-power claw-pole motor. The predicted results compare well with measurements of the prototype motors. The motor design process in this thesis uses a magnetic equivalent circuit (MEC) model of the outer-rotor claw-pole motors that is accurate enough to describe the physics of the electromagnetic conversion. Additional equivalent circuits are made to evaluate the mechanic and thermal loading of the machines. The outcome of the equivalent circuit models is enough to estimate roughly the optimal size of the motor and the motor output according to the materials selected. After the rough design process, which is based on equivalent circuits, is finished, a series of FE magnetostatic analyses are made in order to evaluate the static characteristics of the motors, to specify the magnetization losses and to carry out a sensitivity study for the proposed size of the motors. Finally, the magnetic, mechanic and thermal design is analyzed dynamically and statically by the use of coupled multiphysics. The task of the coupled multiphysics is to find out the cooling capability and the thermal limit of the motor as well as the mechanic stress in the motor parts due to magneto-mechanic loading. It is discussed how the discrepancy between the calculated and measured cogging torque depends on the fineness of the 3D FE air gap mesh. Iron loss estimation based on the results of the FE-analysis is made taking the local rotation, and not only pulsation, of the magnetic flux into consideration. It is shown that the loss coefficients in the material model must be adapted to account for flux rotation. A part from the output of the machine as an electromechanical energy converter is their controllability in the electric drive system. Based on the static characteristics, which are calculated in the FE-analysis and verified in prototype measurements, a tailor made control method is developed for the machines designed. Results are presented of extensive simulations and experimental verifications of the proposed control strategy and power electronic circuitry. The high-speed four-pole single-phase motor shows satisfactory results. The other motor, which has 20 poles and two phases, has a main weakness in its complex assembling and a large cogging torque

Comparison of interior permanent magnet synchronous machines for a high-speed application

Permanent Magnet machines have been increasingly used in high-speed applications due to the advantages they offer such as higher efficiency, output torque and, output power. This dissertation discusses the electrical and magnetic design of permanent magnet machines and the design and analysis of two 10 kW, 30000 rpm Interior Permanent Magnet (IPM) machines. This dissertation consists of two parts: the first part discusses high-speed machine topologies, and in particular the permanent magnet machine. Trends, advantages, disadvantages, recent developments, etc. are discussed and conclusions are made. The second part presents the design, analysis and testing of interior permanent magnet machines for a high-speed application. The machines are designed from first principles and are simulated using Ansys Maxwell software to understand the finite element analysis. In order to obtain a fair comparison between the machines, the required output criteria was used as the judging criteria (10kW, 30000 rpm). As a result, the rotor diameter, stator diameter, airgap length, and stack length were kept the same for both machines. The winding configuration was set as distributed windings, however the number of turns and other details were kept flexible in order to be able to obtain the best design for each machine. Similarly, the magnet volume was kept flexible as this could be used as a comparison criteria relating to the cost of the machines. The two IPM topologies are compared with respect to their torque, magnetic field, airgap flux, core loss, efficiency, and cost. The radial IPM produces a smoother torque output, with lower torque ripple, and has lower losses compared to the circumferential IPM which produces a higher torque and power output. Furthermore, the circumferential IPM also experiences much higher torque ripple and core losses, both of which are highly undesirable characteristics for high-speed machines. In addition, the circumferential IPM has a much more complex manufacturing process compared to the radial IPM which would significantly increase the cost of prototyping the machine, thus the radial IPM was selected for prototyping and brief experimental analysis. The radial IPM has been experimentally tested under no-load conditions. These results were successfully compared to the simulated and analytical results to show correlation between the design and experimental process. Potential areas of further work may include conducting detailed loss analysis to understand the effects that changing various design parameters has on the core loss and overall performance. Detailed thermal and mechanical analysis of the machines may also result in interesting conclusions that would alter the design of the machine to make it more efficient

Study with magnetic property measurement of soft magnetic composite material and its application in electrical machines

This paper reports our study with the magnetic property measurements of soft magnetic composite (SMC) materials under both alternating and rotational magnetic excitations, and development of different electrical machines with SMC cores and three-dimensional magnetic field, such as claw pole and transverse flux motors. Three-dimensional finite element electromagnetic field analysis is conducted for determining some important parameters and optimizing the machine structures. The analysis methods are validated by the experimental results on two SMC motor prototypes

Design of High Efficiency Brushless Permanent Magnet Machines and Driver System

The dissertation is concerned with the design of high-efficiency permanent magnet synchronous machinery and the control system. The dissertation first talks about the basic concept of the permanent magnet synchronous motor (PMSM) design and the mathematics design model of the advanced design method. The advantage of the design method is that it can increase the high load capacity at no cost of increasing the total machine size. After that, the control method of the PMSM and Permanent magnet synchronous generator (PMSG) is introduced. The design, simulation, and test of a permanent magnet brushless DC (BLDC) motor for electric impact wrench and new mechanical structure are first presented based on the design method. Finite element analysis based on the Maxwell 2D is built to optimize the design and the control board is designed using Altium Designer. Both the motor and control board have been fabricated and tested to verify the design. The electrical and mechanical design are combined, and it provides an analytical IPMBLDC design method and an innovative and reasonable mechanical dynamical calculation method for the impact wrench system, which can be used in whole system design of other functional electric tools. A 2kw high-efficiency alternator system and its control board system are also designed, analyzed and fabricated applying to the truck auxiliary power unit (APU). The alternator system has two stages. The first stage is that the alternator three-phase outputs are connected to the three-phase active rectifier to get 48V DC. An advanced Sliding Mode Observer (SMO) is used to get an alternator position. The buck is used for the second stage to get 14V DC output. The whole system efficiency is much higher than the traditional system using induction motor

The integration of input filters in electrical drives

PhD ThesisThe integration of passive components such as inductors and capacitors has gained significant popularity in integrated drive research, and future power electronics systems will require more integrated and standardised packages. These give rise to better power density and improved performance. However, packaging techniques and passive components have been considered a technological barrier which is limiting advances in power electronics. The focus on size reduction should be turned towards the passive components, such as converter chokes, DC-link capacitors and electromagnetic interference (EMI) filters, and achieving greater power density depends on innovative integration concepts, flexibility in structures and extended operating temperature ranges while system integration and modularity are not mutually exclusive. This research considers the possibility of integrating input power filter components into electric machines. Particular attention is paid to the integration of electromagnetic line filter inductors to give better utilisation of the motor volume and envelope. This can be achieved by sharing the machine’s magnetic circuit. An LCL line filter has been chosen to be integrated with a gridconnected permanent magnet synchronous machine. Machines have been proposed in this study for low speed (3000 RPM) and high speed (25000 RPM) operation. The two machines have similar dimensions, but the low-speed machine is less challenging in terms of losses and filter integration, so attention is directed more to the high-speed machine. Both are supplied with low- and high-power drives at power ratings of 4.5 kW and 38 kW respectively. Several novel techniques have been investigated to integrate filter inductors into the electrical machines to produce a single mechanically packaged unit without significant increases in size and losses. Different approaches have been simulated using finite element analysis (FEA) to assess the effectiveness of the integration of passives within the machine structure. Each design has been iteratively optimised to determine the best mass of copper and core for the integrated filter inductors, targeting parity in power density when compared to traditional separate packages. The research demonstrates that an approach utilising a double-slot stator machine (named the integrated double slot (IDS) machine) with input filters wound into the outermost slots is the most appropriate choice in terms of achieving higher power density. The integrated filter inductors mimic the electromagnetic behaviour of the discrete industrially packaged inductors but with a volume reduction of 87.6%. A prototype of the IDS machine design of a 38 kW, 25000 RPM, including filter inductors was manufactured and testedthe General Electricity Company of Libya (GECOL), the Engineering and Physical Sciences Research Council (EPSRC), and the Engineering Doctorate scheme at Newcastle University

In-wheel motors for electric vehicles

PhD ThesisThe in-wheel motor technology as the source of traction for electric vehicles has been researched recently because it is compact and ease-to-integrate. The motor is housed in the wheel. Since the room for the motor is tightly defined by the size of the wheel and there is no gearing system, the motor must have a high torque density to drive the vehicle directly and a high efficiency to keep cool. The existing motor uses a surface-mounted magnet topology. To make it more cost-competitive, the magnet material needs to be reduced while maintaining the torque performance at the rated operating condition. It is the motive of this Ph.D. research. The thesis starts with a brief introduction on the background of the electric vehicle. Then the major challenges of the in-wheel motor technology are summarised. With the derived specifications, an induction machine and a switched reluctance machine are then simulated and analysed. Still, the permanent magnet synchronous machine is proved to have the highest torque density. Change from surface-mounted to interior topology, six new magnet topologies are investigated. The V-shaped interior magnet topology shows superior torque-to-magnet-mass ratio and is easy-to-manufacture. It gives 96% torque while using 56% of the magnet mass compared to the existing motor due to the assist from the additional reluctance torque and the lower magnetic circuit reluctance. The key to use less magnet mass while avoiding the demagnetisation is the front iron shielding effect. The analytical explanation on the better resistance to demagnetisation in the V-shaped motor is provided. The magnet loss mechanism is discussed for proper segmentation. Detailed design adjustments are made to compromise between the torque-to-magnet-mass ratio and the manufactural practicality. Issues regarding to lower mechanical rigidity occurred in initial assembly of the prototype and solutions are proposed. Followed by successful assembly, experimental tests were conducted and results show good agreement with the simulation. A specific form of torque ripple is found in the V-shaped motor and occurs generally in all fractional-slot concentrated-winding machines with saliency. It is explained by an analytical model. This model is also extended to explain the generally lower reluctance torque in vi fractional-slot concentrated-winding machines. Potential design improvements are suggested and simulated for future versions.Protean Electri

An innovative natural air-cooling system technique for temperature-rise suppression on the permanent magnet synchronous machines

Peer ReviewedPostprint (author's final draft