38 research outputs found
A Comparative Study of Yokeless and Segmented Armature versus Single Sided Axial Flux PM Machine Topologies for Electric Traction
This article systematically compares two axial flux permanent magnet machines designed for a university student racing car application: a double-rotor single-stator yokeless and segmented armature (YASA) structure, and a single-stator single-rotor configuration. Both machines are optimized for minimum loss and active weight using three-dimensional finite element analysis and the highest performing candidate designs are compared in more detail. The studies indicate that the benefits offered by the YASA configuration over the single-stator single-rotor machine are achieved only for specific designs that are heavier. For the design space with lower mass, albeit with increased losses, the Pareto front designs overlap. In this envelope, the YASA configuration demonstrates higher efficiencies at higher speeds, whilst the single-stator single-rotor is more efficient in high torque duty cycles. This shows the performance of the two machines is very similar and the choice is application specific. To validate the finite element analysis used in the optimization, a prototype was built and tested. Results showed good alignment between simulation and experimental data
Improving high-speed electrical machines by amorphous metals
This dissertation is about the application of an amorphous magnetic material (AMM) to a sleeve-free interior permanent-magnet (PM) rotor of high-speed synchronous motors. Currently, surface-mounted PM rotors are commonly used in the high-speed motors. In order to protect the high-speed rotors from centrifugal forces, high-strength non-ferromagnetic sleeves are required. This results in a reduced torque density, lowered flux-weakening ability, and highen losses of the motor caused by pulse-width-modulation (PWM) voltage. Hence, a sleeve-free rotor structure is beneficial.
AMM has been used for transformers and inductors for decades. It is well-known due to its low core losses. However, because of its high hardness and brittleness, slotting becomes a key obstacle to its application in electrical machines. Hence, this material has not been widely applied in the electrical machines yet. An important property, the high mechanical strength of the AMM has been ignored eagerly. In this work, an interior PM rotor made from AMM for high-speed operation is studied. The high mechanical strength and the low core losses of the AMM are fully taken use of. Because of the difficulty in slotting of the AMM, this material is not used for the stator and a conventional silicon steel will be used.
In order to fulfill the proposed high-speed rotor, the properties of the AMM in terms of electromagnetics and mechanics are experimentally studied. The influences of the mechanical stress and temperature on the electromagnetic properties of the AMM cores are well studied. Based on the measured data, a prototype is designed and optimized in terms of electromagnetics, mechanics and thermal behaviors. To ensure the success of the prototype, the slotting methods are also investigated and wire electrical discharge machining method is selected for manufacturing of the AMM rotor core. In order to show the advantages and disadvantages of the proposed high-speed AMM rotor, a surface-mounted PM rotor covered by a carbon-fiber sleeve is designed as a comparison. Since the influences of the PWM inverter on the losses of the high-speed motors are significant and this problem has not been thoroughly investigated before, the dissertation goes into a further research on it to fill the gap in this field.
Finally, two prototypes are built and tested. The design results are verified through experiments. It is verified that by applying the AMM to the proposed rotor, the performance of the high-speed PM motor is significantly improved, such as better flux weaking ability, higher torque and power densities and higher efficiency. Based on the tested data of the prototypes, it is confirmed that the AMM has high potential in the application of high-speed high-power-density PM motors
Development and Implementation of a Mouldable Soft Magnetic Composite
Electrical machines, chokes and induction heaters are found in most homes,offices and factories all over the world. They are used to create movement, filtrate the power or to generate heat. A typical unit consist of a coil and a flux conductor material. Some of the materials have been established for over 100 years, while others are only a couple of decades old.A new flux conductor material has been developed at the Division of Production and Materials Engineering at Lund University. The material is called soft magnetic mouldable composite (SM2C). This thesis is focused on investigating the potential of this material and lay a knowledge foundation, wherein the material properties and manufacturing process of the material is tested and further developed, as well as the material composition. In order to use the full potential of the material a holistic view of all the materials involved is necessary. Both coil and insulation suitable for the mouldable soft magnetic composite are therefore studied. Tests are performed both on the separate materials, but also together in applications. Several motors and induction heaters were built and tested in different projects.Results from the work show that by changing from solid copper tubes to litz wire and by using a flux conductor an increase of efficiency from 50-80 % to 98 % is possible. This is due to lower losses in the current conductor and higher flux linkage.The possibility to mould the soft magnetic composite has interesting potential. It is shown that sensors, current conductors and other soft magnetic materials can be integrated directly into the composite. Also, the technology will provide a good thermal contact between the materials. This is especially important for the current conductor, which is usually the main heat source. A good contact will help conduct away the heat if the device is designed properly.Other opportunities are opened with the new technology as well. The size of a moulded part has no limit, unlike for other soft magnetic composites that are usually pressed. It is possible to mould parts into almost any geometry, but it is also easy to machine the material if wanted
SRM drives for electric traction
"GAECE" -- PortadaDescripció del recurs: 11 maig 2020GAECE (Grup d’accionaments elèctrics amb commutació electrònica). The group of electronically commutated electrical drives is a research team of Universitat Politècnica de Catalunya (UPC BARCELONATECH), which conducts investigation in four areas: electrical drives, power electronics, mechanics and energy and sustainability. Regarding electrical drives, research focuses on the development of new reluctance, permanent magnet and hybrid electrical drives. The main goal of those electrical drives is the integration of the power converter/controller and the mechanical transmission, being specially intended for the traction of light electric vehicles. That research is carried out by using the analysis of finite elements, taking into account eco-design criteria, considering new materials and new control strategies.First editio
A review of design optimization methods for electrical machines
© 2017 by the authors. Licensee MDPI, Basel, Switzerland. Electrical machines are the hearts of many appliances, industrial equipment and systems. In the context of global sustainability, they must fulfill various requirements, not only physically and technologically but also environmentally. Therefore, their design optimization process becomes more and more complex as more engineering disciplines/domains and constraints are involved, such as electromagnetics, structural mechanics and heat transfer. This paper aims to present a review of the design optimization methods for electrical machines, including design analysis methods and models, optimization models, algorithms and methods/strategies. Several efficient optimization methods/strategies are highlighted with comments, including surrogate-model based and multi-level optimization methods. In addition, two promising and challenging topics in both academic and industrial communities are discussed, and two novel optimization methods are introduced for advanced design optimization of electrical machines. First, a system-level design optimization method is introduced for the development of advanced electric drive systems. Second, a robust design optimization method based on the design for six-sigma technique is introduced for high-quality manufacturing of electrical machines in production. Meanwhile, a proposal is presented for the development of a robust design optimization service based on industrial big data and cloud computing services. Finally, five future directions are proposed, including smart design optimization method for future intelligent design and production of electrical machines
Design of a high speed high power switched reluctance motor
PhD ThesisAn increase in the price of rare earth materials in 2009 prompted
research into alternative motor technologies without permanent
magnets. The SRMs have become more of an attractive solution as
they are relatively simpler to construct than other machines
technologies hence cost effective. Furthermore, the rugged structure of
the rotor makes it suitable for high speed operation, if appropriately
designed.
This thesis investigates the design, analysis and prototype manufacture
of an SRM, that from electromagnetic point of view, meets the power
output of the PM machine used in the Toyota Prius, although
operating at a higher speed of 50,000 rpm. As a result, the required
torque is considerably less than an equivalent motor with the same
output power running at lower speed, hence this approach allows for
much smaller frame sizes. To achieve the required torque, careful choice
of stator/rotor tooth combination, coil number of turns and number of
phases is needed. Running at high speed, increases the AC copper loss
(consisting of skin effect and proximity effects) and iron loss. These
shortcomings are extensively discussed and investigated.
The mechanical design of this motor requires careful consideration in
order to minimise the high mechanical stresses acting upon the rotor,
which are due to the high radial forces caused by the centripetal force
at high speed. In order to address the mechanical constraints caused by
the hoop stress, a structure common to flywheels is applied to the
rotor. In this approach, the shaft bore is removed and the laminations
are sandwiched together using cheek plates, which are secured using tie
rods. The cheek plates have their extending shafts, which consequently
will transfer the torque to the rest of the system. The proposed model
is analysed for both the electromagnetic and mechanical aspects,
successfully demonstrating a promising rotor topology for the design
speed. A high speed motor design needs to take into account shaft
design, rotor design and bearing design. The high speed operation of
the salient rotor gives dramatic rise to the windage loss. These factors
are carefully considered in this work and the results are presented
Performance of Induction Machines
Induction machines are one of the most important technical applications for both the industrial world and private use. Since their invention (achievements of Galileo Ferraris, Nikola Tesla, and Michal Doliwo-Dobrowolski), they have been widely used in different electrical drives and as generators, thanks to their features such as reliability, durability, low price, high efficiency, and resistance to failure. The methods for designing and using induction machines are similar to the methods used in other electric machines but have their own specificity. Many issues discussed here are based on the fundamental achievements of authors such as Nasar, Boldea, Yamamura, Tegopoulos, and Kriezis, who laid the foundations for the development of induction machines, which are still relevant today. The control algorithms are based on the achievements of Blaschke (field vector-oriented control) and Depenbrock or Takahashi (direct torque control), who created standards for the control of induction machines. Today’s induction machines must meet very stringent requirements of reliability, high efficiency, and performance. Thanks to the application of highly efficient numerical algorithms, it is possible to design induction machines faster and at a lower cost. At the same time, progress in materials science and technology enables the development of new machine topologies. The main objective of this book is to contribute to the development of induction machines in all areas of their applications
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
Investigation of diamagnetic bearings and electrical machine materials for flywheel energy storage applications
Recent trends in energy production have led to a renewed interest in improving grid
level energy storage solutions. Flywheel energy storage is an attractive option for
grid level storage, however, it suffers from high parasitic loss. This study investigates
the extent to which passive diamagnetic bearings, a form of electromagnetic bearing,
can help reduce this parasitic loss.
Such bearings require three main components: a weight compensation mechanism
(lifter-floater), a stabilizing mechanism and an electrical machine. This study makes
use of a new radial modification of an existing linear multi-plattered diamagnetic
bearing. Here a prototype is built and analytical expressions derived for each of the
three main components. These expressions provide a method of estimating
displacements, fields, forces, energy and stiffness in the radial diamagnetic bearing.
The built prototype solution is found to lift a 30 [g] mass using six diamagnetic
platters for stabilization (between ring magnets) with a disc lifter and spherical
floater for weight compensation. The relationship between mass and number of
platters was found to be linear, suggesting that, up to a point, increases in mass are
likely possible and indicating that significant potential exists for these bearings
where high stiffness is not needed – for instance in flywheel energy storage.
The study examines methods of reducing bearing (parasitic) losses and demonstrates
that losses occur in three main forms during idling: air-friction losses, electrical
machine losses, stabilizing machine losses. Low speed (158 [rpm]) air-friction
losses are found to be the dominant loss at 0.1 [W/m3]. The focus of this study,
however, is on loss contributions resulting from the bearing’s electrical machine and
stabilizing machine. Stabilizing machine losses are found to be very low at: 1 ×
10−6 [W/m3] – this leaves electrical machine losses as the dominant loss.
Such electrical machine losses are analysed and divided into eddy current loss and
hysteresis loss. Two components of hysteresis loss are remanent field related cogging
loss and remagetization loss. Eddy current losses in silicon steel laminations in an
electrical machine are quite high, especially at high speeds, with losses in the order
of 1 × 105 [W/m3]. Noting the further high cost of producing single unit quantities
of custom lamination-based electrical machine prototypes, this high loss prompts a
look at potentially lower cost ferrite materials for building these machines. A
commercial sample of soft magnetite ferrite is shown to have equivalent eddy current
losses of roughly 1 × 10−13 [W/m3]. The study notes that micro-structured
magnetite has significant hysteresis loss. Such loss is in the order of 1 ×
10−3 [W/m3] when referring to both remanence related cogging and
remagnetization.
This study, thus, extends its examination of loss to nano-structured magnetite.
Magnetite nano-particles have shown superparamagnetic (no hysteresis) behaviour
that promises the elimination of hysteresis losses. A co-precipitation route to the
synthesis of these nano-particles is examined. A detailed examination involving a
series of 31 experiments is shown to demonstrate only two pathways providing
close-to-superparamagnetic behaviour. After characterization by Scanning Electron
Microscope (SEM), X-Ray Diffractometer (XRD), Superconducting Quantum
Interference Device (SQUID) and crude colorimetry, the lowest coercivity and
remanence found in any given sample falls at −0.17 [Oe] (below error) and
0.00165 [emu/g] respectively. These critical points can be used to estimate
hysteresis related power loss, however, to produce bulk ferrite a method of sintering
or bonding synthesized powder is needed. A microwave sintering solution promises
to preserve nano-structure when taking synthesized powders to bulk material. A set
of proof-of-concept experiments provide the ground work for proposing a future
microwave sintering approach to such bulk material production.
The study uses critical points measured by way of SEM, XRD, SQUID
characterization (e.g. remanence and coercivity) to implement a modified Jiles-Atherton
model for hysteresis curve fitting. The critical points and curve fitting
model allow estimation of power loss resulting from remanent related cogging and
remagnetization effects in nano-structured magnetite. Such nano-structured
magnetite is shown to exhibit hysteresis losses in the order of 1 × 10−4 [W/m3]
from remagnetization and 1 × 10−7[W/m3] from remanence related cogging drag.
These losses are lower than those of micro-structured samples, suggesting that nano-structured
materials have a significant positive effect in reducing electrical machine
losses for the proposed radial multi-plattered diamagnetic bearing solution. The
lower parasitic loss in these bearings suggests excellent compatibility with flywheel
energy storage applications