Line-start permanent-magnet motor single-phase steady-state performance analysis

This paper describes an efficient calculating procedure for the steady-state operation of a single-phase line-start capacitor-run permanent-magnet motor. This class of motor is beginning to be applied in hermetic refrigerator compressors as a high-efficiency alternative to either a plain induction motor or a full inverter-fed drive. The calculation relies on a combination of reference-frame transformations including symmetrical components to cope with imbalance, and dq axes to cope with saliency. Computed results are compared with test data. The agreement is generally good, especially in describing the general properties of the motor. However, it is shown that certain important effects are beyond the limit of simple circuit analysis and require a more complex numerical analysis method

Effect of winding harmonics on the asynchronous torque of a single-phase line start permanant-magnet motor

This paper presents an analytical method for calculating the effect of winding harmonics on the asynchronous torque of a single-phase line-start permanent-magnet motor. The method is an extension of earlier work, which combines symmetrical-component analysis with dq-axis theory to model the various components of forward and backward rotating fields. The effect of individual winding harmonics is brought out both theoretically and experimentally, by comparing calculated and measured torque/speed characteristics for a series of six motors with different distributions of turns in both the main and auxiliary windings

Analytical prediction of the electromagnetic torques in single-phase and two-phase AC motors

The single-phase and two-phase versions of AC motors can be modelled by means of the two-axis (d-q) theory with sufficient accuracy when the equivalent circuit parameters are correctly estimated. This work attempts to present a unified approach to the analytical prediction of the electromagnetic torque of these machines. Classical d-q axes formulation requires that the reference frame should be fixed on the frame where the asymmetries arise, i.e. the stator and rotor. The asynchronous torques that characterize the induction motors are modelled in a stationary reference frame, where the d-q axes coincide with the physical magnetic axes of the stator windings. For the permanent magnet motors, that may exhibit asymmetries on both stator and rotor, the proposed solution includes: a series of frame transformations, followed by symmetrical components decomposition. As in single-phase and two-phase systems the homopolar component is zero; each symmetrical component – negative and positive – is further analysed using d-q axes theory. The superposition principle is employed to consider the magnets and rotor cage effects. The developed models account for the most important asymmetries of the motor configuration. These are, from the stator point of view, different distribution, conductors' dimensions and number of effective turns, non-orthogonal magnetic axes windings and from the rotor point of view, asymmetrical rotor cage, variable reluctance, and permanent magnets effect. The time and space harmonics effect is ignored. Test data are compared with the computed data in order to observe how the simplifying assumptions affect the level of accuracy. The analytical prediction methods make possible torque computation according to the nature of the torque being computed, namely, induction, reluctance and excitation (permanent magnet). The results are available for quasi steady-state, steady-state (rated or synchronous speed) and dynamic analyses. All the developed mathematical models can be used in preliminary design for further optimisation and accurate estimation in complex numerical models. Another important feature of the analytical models for single-phase and two-phase AC motors, is that they can be directly implemented in any suitable electrical drives control strategy.reviewe

Efficient Methods for the Study of Eddy-Currents Effects in Medium-Voltage Rotating Electrical Machines

Lo scopo di questa tesi \ue8 presentare alcuni metodi efficienti (dal punto di vista computazionale) per il calcolo degli effetti dovuti alle correnti parassite (eddy currents) in macchine elettriche rotanti in media tensione. Due applicazioni in particolare sono state considerate nel dettaglio. Inizialmente viene analizzato il fenomeno delle correnti parassite indotte nell'albero di motori asincroni a due poli e il conseguente effetto sulle prestazioni della macchina, focalizzandosi in particolare sul fattore di potenza. La seconda parte della tesi concentra la sua attenzione sullo studio dell'avviamento da rete di motori sincroni con rotore massiccio. Per ciascuna applicazione vengono introdotte alcune procedure di calcolo, facenti uso di opportuni modelli numerici basati sul metodo degli elementi finiti, per mezzo delle quali vengono adeguatamente calcolati i parametri dei circuiti equivalenti di macchina, tenendo conto degli effetti legati alle correnti parassite. I modelli numerici sono opportunamente definiti, in modo tale da ridurre al massimo la complessit\ue0 delle geometrie e il conseguente onere computazionale. I risultati delle procedure innovative qui proposte sono confrontati con i dati provenienti da prove sperimentali sulle macchine oggetto di studio e con analoghi risultati di calcolo dedotti tramite le procedure comunemente utilizzate. Il confronto fra questi dati ha dimostrato che gli approcci di calcolo introdotti in questa tesi permettono di ottenere risultati con un elevato livello di accuratezza e una netta riduzione dell'onere computazionale.The efficient computation of eddy-current effects in medium voltage electric machines is discussed in this dissertation. Two particular cases are considered. Firstly, the effects of shaft eddy-currents on two-pole induction motor performance is addressed, with special focus on the power factor. In the second part of the thesis the start-up calculation of a large synchronous motor with solid rotor is analyzed. For each application a special calculation procedure is introduced. These procedures adopt a set of suitable finite-element models to properly compute the machine equivalent circuit parameters that are mainly influenced by eddy-current-related phenomena. By suitably choosing finite-element models boundary conditions and excitations their geometry is simplified to the maximum possible extent, in order to reduce the computational burden. The results of the new calculation methods are compared with experimental data and with analogous results obtained from commonly-adopted calculation procedures. The comparison proves that the proposed approaches can lead to high accuracy levels with very remarkable computational savings

Comparison of Induction and PM Synchronous motor drives for EV application including design examples

Three different motor drives for electric traction are compared, in terms of output power and efficiency at the same stack dimensions and inverter size. Induction motor (IM), surface-mounted permanent-magnet (PM) (SPM), and interior PM (IPM) synchronous motor drives are investigated, with reference to a common vehicle specification. The IM is penalized by the cage loss, but it is less expensive and inherently safe in case of inverter unwilled turnoff due to natural de-excitation. The SPM motor has a simple construction and shorter end connections, but it is penalized by eddy-current loss at high speed, has a very limited transient overload power, and has a high uncontrolled generator voltage. The IPM motor shows the better performance compromise, but it might be more complicated to be manufactured. Analytical relationships are first introduced and then validated on three example designs and finite element calculated, accounting for core saturation, harmonic losses, the effects of skewing, and operating temperature. The merits and limitations of the three solutions are quantified comprehensively and summarized by the calculation of the energy consumption over the standard New European Driving Cycl

Starting performance of synchronous motors

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High frequency losses in induction motors, part 2

The following subject areas are covered: high frequency losses in induction motors; stray losses in induction motors; and high frequency time harmonic losses in induction motors

Performance analysis for a shaded-pole linear induction motor

Bibliography: pages 129-148.The induction motor remains the prime mover of present day industry with it's associated components in drive applications. In many such applications, fractional horse-power motors find ready use in small mechanisms where three-phase power supply is not available. In Southern Africa, these motors can be used is rural areas with simple reticulation systems, hence the renewed interest in the development of these low-power electrical motors, especially specialised models such as linear versions of such motors for special applications. This research is in the area of single-phase LIMs. The objective has been to model the shaded-pole LIM, in an attempt to enhance it's performance through improved design methods. This was carried out using an integrated analysis approach, involving circuital and field theory in the analysis of the practical motor, and computer simulation of it's equivalent model using the finite element method. Linear counterparts are possible for all the various forms of rotating electrical machines. All cylindrical machines can be 'cut' along a radial plane and 'unrolled' [32]. LIMs convert electrical energy directly into mechanical energy of translatory motion. Some advantages of linear version of induction motors are: they are gearless and often require minimal material thus minimising cost. While their scope of application are somewhat limited when compared to rotary versions, they do however give excellent performance in special situations where translator motion is required. However, the output power-to-mass and output power-to-volume of active materials ratio is reduced compared to rotary induction motors[45]. These disadvantages are caused by the large air-gap and the open magnetic circuit, which produces parasitical effects

Disc-geometry reluctance motors

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