1,721,003 research outputs found
Advanced design of direct drive PM machines
Full text linkThe following thesis takes into consideration some aspects regarding the design of permanent magnet machines.
The growing interest in this type of emachines is due to certain characteristics that they present: high torque density, possibility of eliminating the gear-box and then subsequent reduction of costs and maintenance, etc..
Many applications are found in the field of wind generators, electric traction and rope traction.
The special construction of such machines, such as the presence of fractional-slot windings, the large size and large powers that they may present, lead to the need of considering some issues often not properly investigated during the machine design.
To this aim, the thesis examines the following two aspects: the rotor losses in machines with fractional-slot windings and the fault tolerance.Il seguente lavoro di tesi prende in considerazione alcuni aspetti riguardanti il progetto di macchine a magneti permanenti.
Il crescente interesse rivolto a questo tipo di macchine è dovuto ad alcune caratteristiche che esse presentano: alta densità di coppia, possibilità di eliminazione del riduttore di giri e quindi conseguente riduzione di costi e manutenzione, ecc.
Molte applicazioni si trovano nel campo della generazione eolica, della trazione elettrica e della trazione a fune.
Le particolarità costruttive di tali macchine, quali ad esempio la presenza di avvolgimenti a cave frazionarie, le notevoli dimensioni e le grosse potenze che esse possono presentare, portano a dover considerare alcune problematiche spesso non propriamente investigate durante la progettazione.
A questo scopo, il lavoro di tesi analizza i seguenti due aspetti: le perdite rotoriche in macchine con avvolgimenti frazionari e la tolleranza ai guasti
Impact of MMF Space Harmonic on Rotor Losses in Fractional-Slot Permanent-Magnet Machines
No full textAbstract—The fractional-slot permanent-magnet (PM) ma-
chines are used in many applications due to their high torque
density, low torque ripple, and high efficiency. However, the
fractional-slot machines are characterized by high contents of
space harmonics in the air-gap MMF distribution. Such harmonics
cause flux variation in the air gap, and the main consequence is the
induced losses in the rotor. Depending on the combination of slots
and poles of the machine, there are different harmonic contents
and then rotor losses. By means of a simple model of the rotor
losses, this paper investigates the link between the rotor losses and
the combination of the slots and the poles of the fractional-slot PM
machines
Index of rotor losses in three-phase fractional-slot permanent magnet machines
No full textAbstract: The aim of here is to define an index of the rotor losses induced by the magnetomotive force (MMF)
space harmonics in fractional-slot permanent magnet (PM) machines. Such an index facilitates a rapid
discrimination of the various fractional-slot PM machines, based on the numbers of slots and poles. For the
sake of generality, a simple model of the rotor losses is adopted to compute such an index of rotor losses.
However, the index behaviour follows that of rotor losses computed by means of more complex models
Thermal Analysis of a Five-Phase Motor Under Faulty Operations
No full textThis paper describes the thermal behavior of a five-phase permanent-magnet motor during the postfault control strategy, considering the open-circuit fault of both one and two phases. Proper current control strategies are applied to get proper performance under faulty operating conditions. The current of the healthy phases is contextually increased to get a higher average torque, but maintaining the same Joule losses of the healthy case. It is shown that such increase on the average current does not affect the thermal dissipation, and the motor can continue to operate properly also in faulty conditions. Experimental results confirm the simulation predictions
Effect of Stator and Rotor Saturation on Sensorless Rotor Position Detection
No full textThis paper investigates the impact of the geometry of a permanent-magnet (PM) motor on the capability to detect the rotor position without sensors by means of a high-frequency signal injection. An interior PM motor with three rotor flux barriers is considered, which is characterized by a magnetic saliency, necessary for the sensorless rotor position detection. The objective is twofold: 1) to keep an adequate saliency in all the operating range of the motor, including operations at high current, and 2) to limit the angular error of the rotor detection, which is due to the effect of the cross-saturation between the d- and the q-axes. The phenomenon of iron saturation is deeply analyzed, highlighting how the saturation of both the stator and rotor affects the machine performance, in terms of sensorless rotor position detection capability. To this purpose, the motor geometry is modified so as to achieve a higher iron saturation in the stator and, then, in the rotor. Then, the volume of the PM is changed so as to emphasize the impact of the PM flux. Different rotor geometries are finally compared with the initial one
Space vector harmonic analysis of a five-phase PM motor including asymmetries
No full textThis paper deals with the harmonic analysis of the orthogonal space vector components of a five-phase machine. It gives a complete analysis of the harmonic contents of the resulting space vector, considering both symmetric and asymmetric systems. Then, the impact of some phase asymmetries on the space vector harmonic contents is investigated. Therefore the results achieved in such a study will be of reference for determining a fault diagnosis procedure
Sensorless Capability of Fractional-Slot Surface-Mounted PM Motors
Full text linkThis paper investigates the capability of sensorless rotor position detection by means of injection of a high-frequency (HF) signal of fractional-slot surface-mounted permanent-magnet (PM) motors. In order to create an HF anisotropy, such motors are characterized by the presence of a ring around each pole. For the sake of completeness, different windings are considered: a distributed coil winding and a concentrated coil winding. The effect of eddy currents in the magnets, due to the HF signal, is also considered. The effect of the slot opening is also taken into consideration. Finally, the comparison with two different PM rotor topologies is addressed: an interior PM motor and an INSET motor
Considerations on Selecting Fractional-Slot Nonoverlapped Coil Windings
No full textThis paper focuses on the selection of a fractional-slot winding for permanent-magnet (PM) machines. The choice of the proper combination of the number of slots and number of poles, together with the corresponding winding layout, has a strong impact on the PM machine performance, in terms of torque density, torque ripple, magnetomotive force harmonic content, and induced rotor losses, as well as the capability to limit the short-circuit current and other fault-tolerance features. Considering these characteristics, this paper aims to help the PM machine designer to select the proper winding configuration, giving useful indications. The winding choice criteria are given using analytical equations, so that their implementation is easy. In this way, the collection of such criteria becomes a helpful tool in the design process
Analysis and experimental tests of the sensorless capability of a fractional-slot inset PM motor
No full textThe sensorless techniques based on high-frequency signal injection to determine the rotor position is applied to an inset permanent-magnet (PM) motor, whose rotor is characterized by small iron teeth between each couple of PMs. Although these rotor teeth, which are centered along the q-axis, do not significantly contribute to torque production, they yield appropriate rotor saliency to be exploited for the rotor position sensorless detection. The inset PM motor considered in this paper is characterized by a fractional-slot stator, i.e., by a fractional number of slots per pole and per phase. Such a solution is commonly used when a surface-mounted PM machine is considered since it exhibits a higher torque density. A 12-slot 8-pole inset PM motor is investigated as far as its self-sensing capability. Both finite-element analysis and experimental measurements are presented, showing satisfactory agreement. It is shown that the prototype of the inset PM motor available in the laboratory exhibits a good capability to be controlled by sensorless techniques. However, a negative effect is recognized by a nonnegligible ripple of torque and flux linkages. They affect the dynamic performance of the PM motor drive
Design of Synchronous Reluctance Motor for Hybrid Electric Vehicles
No full textThis paper deals with the design of a synchronous reluctance motor suited for hybrid electric vehicles. The focus is mainly on rotor design: the angles of the flux barrier ends are chosen with the aim of reducing the torque ripple due to the slot harmonics. A comparison among different rotor arrangements (one, two, and three flux barriers per pole) is presented. Furthermore, an improvement in terms of low ripple and high average torque is given owing to the "Machaon" configuration. The current vector control method is used to maximize the torque according to the voltage and current constraints, taking into account the saturation effects. The impact of the electrical design on the mechanical characteristics of the rotor (natural frequencies) is discussed as well. At last, the predicted mechanical characteristics of the reluctance motor are presented: torque versus speed behavior, power losses, and power factor. The efficiency map of the machine is also reported in the whole operating region
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