Design of segmental rotor and non-overlap windings in single-phase fefsm for low torque high speed applications

In this research, a new structure of single-phase field excitation flux switching motor (FEFSM) using segmental rotor structure and non-overlap windings arrangement is proposed in order to overcome the drawbacks of low torque and small power performances due to their longer flux path in the single-phase FEFSM using salient rotor structure and overlap windings arrangement. The objectives of this study are to design, analyse and examine performance of the proposed motor, to optimize the proposed motor for optimal performances, and to develop the proposed motor prototype for experimental performance validation. The design and analyses thru 2Dfinite element analysis (FEA) is conducted using JMAG Designer version 15, while deterministic optimization method is applied in design optimization process. To validate the 2D-FEA results, the motor prototype is developed and tested experimentally. Based on various rotor poles analysis, a combination of 12 pole 6 pole (12S-6P) has been selected as the best design due to their highest torque and power capability of 0.91 Nm and 277.4 W, respectively. Besides, the unbalance armature magnetic flux of the proposed FEFSM using segmental rotor has been resolved by using segmental rotor span refinement. The balanced armature magnetic flux amplitude ratio obtained is 1.002, almost 41.2% reduction from the initial design. In addition, the optimized motor has increased maximum torque and power by 80.25% to 1.65 Nm, and 43.6% to 398.6W, respectively. Moreover, copper loss of the optimized design has decreased by 9.7%%, hence increasing the motor efficiency of 25.3%. Finally, the measured results obtained from the prototype machine has reasonable agreement with FEA results, proving their prospect to be applied for industrial and home appliances

Advanced Ultra-High Speed Motor for Drilling

Three (3) designs have been made for two sizes, 6.91 cm (2.72 inch) and 4.29 cm (1.69 inch) outer diameters, of a patented inverted configured Permanent Magnet Synchronous Machines (PMSM) electric motor specifically for drilling at ultra-high rotational speeds (10,000 rpm) and that can utilize advanced drilling methods. Benefits of these motors are stackable power sections, full control (speed and direction) of downhole motors, flow hydraulics independent of motor operation, application of advanced drilling methods (water jetting and abrasive slurry jetting), and the ability of signal/power electric wires through motor(s). Key features of the final designed motors are: fixed non-rotating shaft with stator coils attached; rotating housing with permanent magnet (PM) rotor attached; bit attached to rotating housing; internal channel(s) in a nonrotating shaft; electric components that are hydrostatically isolated from high internal pressure circulating fluids ('muds') by static metal to metal seals; liquid filled motor with smoothed features for minimized turbulence in the motor during operation; and new inverted coated metal-metal hydrodynamic bearings and seals. PMSM, Induction and Switched Reluctance Machines (SRM), all pulse modulated, were considered, but PMSM were determined to provide the highest power density for the shortest motors. Both radial and axial electric PMSM driven motors were designed with axial designs deemed more rugged for ultra-high speed, drilling applications. The 6.91 cm (2.72 inch) OD axial inverted motor can generate 4.18KW (5.61 Hp) power at 10,000 rpm with a 4 Nm (2.95 ft-lbs) of torque for every 30.48 cm (12 inches) of power section. The 6.91 cm (2.72 inch) OD radial inverted motor can generate 5.03 KW (6.74 Hp) with 4.8 Nm (3.54 ft-lb) torque at 10,000 rpm for every 30.48 cm (12 inches) of power section. The 4.29 cm (1.69 inch) OD radial inverted motor can generate 2.56 KW (3.43 Hp) power with 2.44 Nm (1.8 ft-lb) torque at full speed 10,000 rpm for every 30.48 cm (12 inches) of power section. Operating conditions are 300 voltage AC at the motor leads. Power voltage losses in the cables/wirelines to the motor(s) are expected to be about 10% for 5000 feet carrying 2 amperes. Higher voltages and better insulators can lower these losses and carry more amperes. Cutting elements for such high tip velocities are currently not available, consequently these motors will not be built at this time. However, 7.62 cm (3 inch) OD, low speed, PMSM radial electric motors based on this project design are being built under a 2006 Oklahoma Center for the Advancement of Science and Technology 'proof of concept' grant

In-wheel Motors: Express Comparative Method for PMBL Motors

One of the challenges facing the electric vehicle industry today is the selection and design of a suitable in-wheel motor. Permanent Magnet Brushless (PMBL) motor is a good choice for the in-wheel motor because of its lossless excitation, improved efficiency, reduced weight and low maintenance. The PMBL motors can be further classified as Axial-Flux Twin-Rotor (AFTR) and Radial-Flux Twin-Rotor (RFTR) machines. The objective of this dissertation is to develop a fast method for the selection of appropriate in-wheel motor depending on wheel size. To achieve this, torque equations are developed for a conventional single-rotor cylindrical, twin-rotor axial-flux and twin-rotor radial-flux PMBL motors with slot-less stators based on magnetic circuit theory and the torque ratio for any two motors is expressed as a function of motor diameter and axial length. The theoretical results are verified, on the basis of magnetic field theory, by building the 3-dimensional Finite Element Method (FEM) models of the three types of motors and analyzing them in magnetostatic solver to obtain the average torque of each motor. Later, validation of software is carried out by a prototype single-rotor cylindrical slotted motor which was built for direct driven electric wheelchair application. Further, the block diagram of this in-wheel motor including the supply circuit is built in Simulink to observe the motor dynamics in practical scenario. The results from finite element analysis obtained for all the three PMBL motors indicate a good agreement with the analytical approach. For twin-rotor PMBL motors of diameter 334mm, length 82.5mm with a magnetic loading of 0.7T and current loading of 41.5A-turns/mm, the error between the express comparison method and simulation results, in computation of torque ratio, is about 1.5%. With respect to the single-rotor cylindrical motor with slotless stator, the express method for AFTR PMBL motor yielded an error of 4.9% and that of an RFTR PMBL motor resulted in an error of -7.6%. Moreover, experimental validation of the wheelchair motor gave almost the same torque and similar dynamic performance as the FEM and Simulink models respectively

Investigation of six-phase surface permanent magnet machine with typical slot/pole combinations for integrated onboard chargers through methodical design optimization

This article presents an analytical magnetic equivalent circuit (MEC) modeling approach for a six-phase surface-mounted permanent magnet (SPM) machine equipped with fractional slot concentrated winding (FSCW) for integrated onboard chargers. For the sake of comparison, the selected asymmetrical six-phase slot/pole combinations with the same design specifications and constraints are first designed based on the parametric MEC model and then optimized using a multiobjective genetic algorithm (MOGA). The commercial BMW i3 design specifications are adopted in this article. The main focus of this study is to achieve optimal design of the SPM machine considering both the propulsion and charging performances. Thus, a comparative study of the optimization cost functions, including the peak-to-peak torque ripple and core losses under both motoring and charging modes and electromagnetic forces (EMFs) under charging, is conducted. In addition, the demagnetization capability in the charging mode and the overall cost of the employed machines are optimized. Since the average propulsion torque is crucial in electric vehicle (EV) applications, it is maintained through the design optimization process. Furthermore, finite element (FE) simulations have been carried out to verify the results obtained from the analytical MEC model. Eventually, the effectiveness of the proposed design optimization process is corroborated by experimental tests on a 2-kW prototype system

Self-starting interior permanent magnet motor drive for electric submersible pumps

The interior permanent magnet (IPM) motor drive has evolved as the most energy efficient technology for modern motion control applications. Electric submersible pumps (ESPs) are electric motor driven fluid recovery systems. ESPs are widely used for producing oil and gas from deep downhole reservoirs. Standard ESPs are driven by classical squirrel cage induction motors (IMs) due to its self-starting capability from a balanced 3-phase ac excitation, ruggedness, simplicity, low cost and wide scale availability. Although there has been a tremendous growth in the design and development of highly efficient and reliable IPM motors for traction drive systems, application of the IPM motor technology in ESPs is still in its infancy due to challenges associated with the design and control of IPM motors. In this thesis, a new self-starting, efficient and reliable IPM motor drive technology is proposed for ESP systems to extend their efficiency, longevity and performance. This thesis investigates two different types of self-starting interior permanent magnet (IPM) motors: cage-equipped IPM motors known as line-start IPM motors and a new type of hybrid self-starting motors called hysteresis IPM motors. The limited synchronization capability of line-start IPM motors for high inertial loads is explained in this thesis. To overcome the starting and synchronization problems associated with line-start IPM motors, a new type of hybrid hysteresis IPM motor is proposed in this thesis. Equivalent circuit modeling and finite element analysis of hysteresis IPM motors are carried out in this thesis. A prototype 2.5 kW hysteresis IPM motor is constructed and experimentally tested in the laboratory. In order to limit the inrush current during starting, a stable soft starter has been designed, simulated and implemented for variable speed operations of the motor. The simulation and experimental results are presented and analyzed in this thesis. Self-starting IPM motors suffer from hunting induced torsional oscillations. Electric submersible pumps are vulnerable against sustained hunting and can experience premature failures. In this thesis, a novel stator current signature based diagnostic system for detection of torsional oscillations in IPM motor drives is proposed. The diagnostic system is non-intrusive, fast and suitable for remote condition monitoring of an ESP drive system. Finally, a position sensorless control technique is developed for an IPM motor drive operated from an offshore power supply. The proposed technique can reliably start and stabilize an IPM motor using a back-emf estimation based sensorless controller. The efficacy of the developed sensorless control technique is investigated for a prototype 3-phase, 6-pole, 480V, 10-HP submersible IPM motor drive. In summary, this thesis carried out modeling, analysis and control of different types of self-starting IPM motors to assess their viability for ESP drive systems. Different designs of self-starting IPM motors are presented in this thesis. In future, a fully scalable self-starting IPM motor drive will be designed and manufactured that can meet the industrial demands for high power, highly reliable and super-efficient ESP systems

Permanent Magnet Machine Design with Cold Spray Magnets

With the global trend toward electrification of transport, the interest in various configurations of electric motors is growing. Surface permanent magnet synchronous machines (SPMSM) are used in many high-performance applications due to low inertia, high torque density, and overload capability. Several applications require low torque pulsations as they can lead to mechanical vibrations and acoustic noise in the electric motor. Various techniques have been proposed in the literature to reduce the torque pulsations either by using machine control strategies or by machine design. Optimization of the rotor permanent magnet (PM) shape is one of the effective methods for reducing torque pulsations. Unfortunately, the low versatility of the motor magnet fabrication technologies limits the development of new motor geometries. Current techniques used for the assembly of PMs in motors such as adhesives, slots, or screws are complex, labor-intensive, and offer very little flexibility for advanced motor design geometries. Consequently, alternative fabrication techniques such as cold spray additive manufacturing are worth exploring. Cold spray additive manufacturing is used for shaping PMs for the direct fabrication of electric motor parts without the need for additional assembly steps. This novel technique allows an increase in the design flexibility of electrical machine geometries targeting improved performance. In this thesis, the PM rotors considered are the conventional rectangular-shaped with unskewed magnets (Model A), skewed magnets (Model B), and sinusoidal-petal-shaped magnets (Model C) along the axial direction. The magnitude of magnetization current pulse required to magnetize these rotors is calculated using an FEA package and an impulse magnetizer setup is designed and prototyped for in-situ magnetization. Various stator terminal connection configurations are analyzed and compared for the magnetizer. The performance of the shaped cold sprayed permanent magnet rotors and their effects on back EMF, electromagnetic torque, and cogging torque are analyzed experimentally and comparisons are made between the different rotor designs. Laminated electrical silicon steel sheets are mainly used to produce the stator and rotor core of an electrical machine. In comparison, there are soft magnetic composites (SMC) which consist of a high purity fine iron powder particle coated with the insulation material. Hence, its electrical resistance is much higher than that of laminated steel. Its isotropic magnetic and physical properties help flux to conduct in a three-dimensional direction and effectively dissipate the heat produced from core losses. The product developed using SMC material uses compaction, heating, and pressing techniques to achieve the desired shape and final size of the machine core parts. Hence, the material wastage is lower as compared to the laminated steel core. In this thesis, the impact of a few manufacturing parameters on SMC properties to ensure that optimized motor performance is achieved was analyzed using three SMC different materials (A, B, and C) using FEA software. Furthermore, machine design parameters are tuned to achieve optimal flux weakening. Finally, an FEA-based performance analysis of a 7.12 kW radial flux PMSM with laminated steel and SMC stator core is used to estimate the torque density and losses in the machines. Two different designs of 24/20 slot-pole and 12/8 slot-pole configuration using conventional surface permanent magnet rotor designs are considered. In addition, the ring-type Halbach-array PM rotor fabricated using cold spray additive manufacturing for 12/8 slot-pole is analyzed and optimized with the SMC stator core for high-speed electric vehicle application

A new modulated permanent magnet twin stator machine for high torque density and better magnet utilisation

PhD ThesisGiven the recent interest in the replacement of internal combustion engines with electric machines, the main aim of this research is to design a high torque density permanent magnet machine to an electric vehicle’s specification. A new design concept for increasing the torque density of a conventional permanent magnet machine is introduced and described theoretically and mathematically. The proposed method involves splitting the stator teeth in order to introduce a magnetic gear ratio into the torque equation. The introduced machine is also further modified to improve its magnet utilisation. An investigation is carried out on the impact of different slot to pole combinations on torque density and an optimum combination found. Thereafter, two optimisation methods are applied. The first method is carried out manually by varying a single parameter and investigating its effect on torque density. The second method is conducted automatically using OptiNet to validate the results achieved with the manual optimisation. Further analysis is carried out, including mechanical evaluation against centrifugal forces in order to determine the mechanical strength of the rotor. Finally, a prototype is constructed and tested with detailed discussion on the results achieved and comparison with finite element calculations in order to validate the design and determine its level of performance. The final design is then compared to the Toyota Camry and Prius electrical motors

A high torque density, direct drive in-wheel motor for electric vehicles

PhD ThesisThe use of in-wheel motors, often referred to as hub motors as a source of propulsion for pure electric or hybrid electric vehicles has recently received a lot of attention. Since the motor is housed in the limited space within the wheel rim it must have a high torque density and efficiency, whilst being able to survive the rigours of being in-wheel in terms of environmental cycling, ingress, shock, vibration and driver abuse. Part of the work of this PhD involved an investigation into different slot and pole combinations in order determine a superior machine design, within given constraints based upon an existing in-wheel motor drive built by Protean Electric. Finite element analysis and optimisation have been applied in order to investigate the machine designs and achieve the optimum combination. The main work of this PhD, presents a high torque dense machine employing a new method of construction, which improves the torque capability with a smaller diameter, compared to that of the existing Protean in-wheel drive system. The machine is designed with an open slot stator and using magnetic slot wedges to close the slots. Having an open slot stator design means the coils can be pre-pressed before being inserted onto the stator teeth, this improves the electrical loading of the machine as the fill factor in the slot is increased. The electromagnetic impact of the slot wedges on the machine design has been studied, also a method of coil pressing has been studied and the impact upon coil insulation integrity verified. To ensure adequate levels of functional safety are met it is essential that failures do not lead to loss of control of the vehicle. Studies on a fault tolerant concept which can be applied to the design of in-wheel motors are presented. The study focuses on the ability to sustain an adequate level of performance following a failure, while achieving a high torque density. A series of failures have been simulated and compared with experimental tests conducted on a Protean motor. Finally a prototype is constructed and tested to determine the true level of performance. The prototype is compared to a new motor built in-house by Protean and achieves an improved level of performance.Protean Electri