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Electric Power Applications, IET

Issue 4 • Date April 2010

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Displaying Results 1 - 9 of 9
  • Editorial

    Publication Year: 2010 , Page(s): 213
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (70 KB)  

    In July 1996, when I agreed to become one of the two Honorary Editors of the IEE Proceedings on Electric Power Applications, I had it in mind to serve in that role for no more than three years. I have often asked myself why I carried on so long. I suppose that there is no simple answer. Clearly I have enjoyed it, but in addition it has enabled me to gain an aerial view of the changes that have taken place in my chosen field of specialisation. View full abstract»

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  • Fault model and performance evaluation of an inverter-fed permanent magnet synchronous motor under winding shorted turn and inverter switch open

    Publication Year: 2010 , Page(s): 214 - 225
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1660 KB)  

    To analyse influences under various fault conditions, a fault model of an inverter-fed permanent magnet (PM) synchronous motor drive that can be used for a performance assessment of a diagnostic algorithm is presented. For fault conditions of a drive system, a short-circuited turn in the stator winding, switching device open in pulse width modulated inverter and the isolation between the inverter and motor are considered. Even though the conventional dq model is widely used to control an AC motor, it cannot be used directly for the analysis of a motor fault, since three-phase balanced condition does not hold under such conditions, and thus, it is not easy to obtain phase voltage inputs of motor from the pole voltage. To overcome this limitation, a fault model of an inverter-fed PM synchronous motor is derived using the line voltage, which can be effectively used to evaluate the performance of a fault detection algorithm. A test motor producing short-circuited turn in the stator winding is built. The validity of the proposed fault model is verified through the comparative simulations and experiments using digital signal processor TMS320F28335 under various fault conditions. View full abstract»

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  • Design and implementation of a novel high-performance sensorless control system for interior permanent magnet synchronous motors

    Publication Year: 2010 , Page(s): 226 - 240
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1146 KB)  

    This study proposes a novel high-performance rotor position estimator for an interior permanent magnet synchronous motor (PMSM). By suitably processing the mathematical model of the motor, a systematic method of the rotor position estimating method has been developed. The proposed control system can be used in the space vector pulse-width modulation switching method, which is widely used in industry. By measuring the DC-bus voltage and the phase currents, a systematic rotor position estimator has been developed. Finally, the rotor position and rotor speed are obtained, and a closed-loop control system can be achieved. A digital signal processor, TMS 320F2812, is used to execute the estimating algorithm and control algorithm. As a result, the hardware is very simple. Several experimental results show that both the position control system and the adjustable speed control system are achieved. The system can be adjusted from 1 to 2000 r/min. In addition, by using the proposed position-loop H ?? controller, the position control system can be achieved with satisfactory performance. This study proposes a new method for a sensorless interior PMSM control system. View full abstract»

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  • Study on rotor structure with different magnet assembly in high-speed sensorless brushless DC motors

    Publication Year: 2010 , Page(s): 241 - 248
    Cited by:  Papers (3)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (930 KB)  

    High-speed permanent magnet (PM) brushless DC motors have gained more and more interests for many applications. The technique of detecting the electromotive force (EMF) zero-crossings is a common method in sensorless operation of PM brushless DC motors. However, the zero-crossings of the phase EMF will be obscured and the sensorless control will be malfunctioned, since the free-wheeling diode conduction can last more than 30 elec-degs under high-speed condition. Therefore it is supposed that the utilisation of third-harmonic EMF is more preferable, as it is not influenced by the free-wheeling diode conduction. Some design features for the high-speed sensorless operation are presented, primarily focusing on the rotor structure with different magnet assembly. The influence of the pole-arc to pole-pitch ratio on the third-harmonic airgap field will be analysed with both finite-element method and analytical model. Based on these analyses, another method which can improve both the third harmonic and fundamental components in the airgap field, by segmenting the parallel-magnetised PMs, is employed and studied. Motor prototypes are then designed and fabricated, and the experimental results confirm the validity of the proposed design method. View full abstract»

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  • Saliency ratio derivation and optimisation for an interior permanent magnet machine with concentrated windings using finite-element analysis

    Publication Year: 2010 , Page(s): 249 - 258
    Cited by:  Papers (13)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1058 KB)  

    The implementation of concentrated windings in interior permanent magnet (IPM) machines has numerous advantages over distributed windings, with a major disadvantage being the decrease in saliency ratio. Theoretically, this would result in a lower field weakening range which is undesirable for traction applications. Although it is revealed in some studies that concentrated winding results in lower saliency ratio, experimental techniques used for accurately acquiring the saliency ratio of IPM machines with concentrated windings are yet to be fully understood. This study presents a proposed finite-element (FE) method, which is derived from the experimental AC standstill test method. With this method, the d- and q-axis inductances (L d and L q) of the IPM machine with fractional-slot concentrated windings can be accurately determined. Limitations of this method are discussed. Subsequently, this method is used to determine L d and L q of various winding configurations and rotor designs. From repeated FE testing using Flux2D, the authors derive a set of general rules for optimising the saliency of an IPM machine with fractional-slot, single-layer concentrated winding. View full abstract»

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  • Computation of additional losses due to rotor eccentricity in electrical machines

    Publication Year: 2010 , Page(s): 259 - 266
    Cited by:  Papers (9)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (711 KB)  

    This study investigates the effect of eccentric rotor on the power losses in electrical machines. The investigations are carried out for an induction machine with PWM-voltage supply and in the cases of dynamic and static eccentricity. The time-stepping two-dimensional finite element method, with coupled field and circuit equations, is used for the simulations. The iron losses are computed through a dynamic loss model. It is shown that the operation of the machine under eccentricity fault results in an increase of both resistive and iron losses. Further the eccentricity causes additional torque modulation and unbalance magnetic pull that result in additional bearing friction losses and wearing. View full abstract»

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  • Integration of non-linear H and sliding mode control techniques for motion control of a permanent magnet synchronous motor

    Publication Year: 2010 , Page(s): 267 - 280
    Cited by:  Papers (5)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (800 KB)  

    A new method using non-linear H and sliding mode control (SMC) is presented for a permanent magnet synchronous motor (PMSM) position control system. It is a high-performance controller in the presence of motor parameters variations and unknown load torque disturbances. In the proposed technique, the load torque is considered as an external disturbance and non-linear H is utilised to minimise its influence on the rotor position. Although H is to some extend robust against motor parameter variations, parameter variations may affect the performance of H controller, so SMC is used to reject these variations. Integration of these two methods offers an efficient robust position controller for PMSM. Position control of PMSM using the proposed method is compared with those obtained by other methods. Merits of the approach through simulations are verified by the experimental results. View full abstract»

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  • Discriminating broken rotor bar from oscillating load effects using the instantaneous active and reactive powers

    Publication Year: 2010 , Page(s): 281 - 290
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (513 KB)  

    A new strategy for detection and diagnosis of broken bars and load oscillations is proposed. The proposed technique is based on the analysis of the instantaneous active and reactive powers spectra, and allows the correct distinction between broken rotor bars and low-frequency load oscillations. A suitable fault severity factor is also proposed, which allows the broken rotor bar fault quantification, while being practically independent of the motor load. By using the proposed technique, a broken bar fault can be detected and diagnosed, even in the presence of load oscillations at frequencies next to twice the slip frequency. Extensive experimental results, both from laboratory and industrial cases, validate the proposal. View full abstract»

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  • Analysis of synchronous reluctance machine with magnetically coupled three-phase windings and reactive power compensation

    Publication Year: 2010 , Page(s): 291 - 303
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1363 KB)  

    Synchronous reluctance machine with simple salient rotor is known to have poor power factor because of its poor reactance ratio. This study presents the use of an auxiliary winding attached to a balanced capacitor to improve the effective reactance ratio as well as the performance characteristics of synchronous reluctance machine. A unique feature of this configuration is that although the machine runs at synchronous speed, the effective reactance ratio of the machine can be improved by appropriate sizing of the capacitor attached to the auxiliary winding, with the constraint of the ampere turn rating of the auxiliary winding. The operational characteristics of a simple salient rotor synchronous reluctance machine equipped with this configuration were investigated and shown to have a desirable performance. How the effective reactance ratio, power factor and airgap flux distribution depend on the size of capacitor attached to the auxiliary winding is determined using a simplified mathematical model of the system. Analytical results and experimental measurements are in good agreement, and demonstrate the effectiveness and benefits of the configuration. View full abstract»

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