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Electric Power Applications, IEE Proceedings -

Issue 3 • Date May 1996

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Displaying Results 1 - 12 of 12
  • Calculation and measurement of unbalanced magnetic pull in cage induction motors with eccentric rotors. II. Experimental investigation

    Publication Year: 1996 , Page(s): 202 - 210
    Cited by:  Papers (16)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (788 KB)  

    For pt.I see ibid., vol.143, no.3, p.193-201 (1996). The paper describes an experimental investigation into the behaviour of a cage induction motor with a statically eccentric rotor. The experimental equipment used allowed for the variation of the eccentricity and the direct measurement of the unbalanced magnetic pull (UMP). The effects of parallel connections of the stator windings and the damping nature of the cage rotor are investigated. The results are used to verify the accuracy of an analytical model derived elsewhere and the correlation between the measured and predicted UMP is found to be good View full abstract»

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  • Series-parallel load-resonant converter for controlled-current arc welding power supply

    Publication Year: 1996 , Page(s): 211 - 218
    Cited by:  Papers (13)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (816 KB)  

    An arc welding power supply requires the ability to limit the load current under short circuit conditions and limit the load voltage under open circuit conditions. The series-parallel load-resonant power converter is a circuit configuration which can achieve this. The potential for high frequency operation in these converters minimises the size of the magnetic components in the power converter and reduces output current ripple. The paper presents the theoretical and practical aspects of the design and construction of a series-parallel load-resonant power converter, for use as a controlled current arc welding power supply. A power converter with an output voltage of 25 V and output current of 200 A operating at 85 kHz is designed and constructed. A novel method of control of the resonant power converter is described. Output power control is achieved by using an active rectifier modulating the DC supply voltage to the power converter. Practical results of the power converter in operation supplying 200 A to a low inductance load are presented View full abstract»

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  • Simplified control method for the single-phase active power filter

    Publication Year: 1996 , Page(s): 219 - 224
    Cited by:  Papers (60)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (468 KB)  

    A simplified control method for the single-phase active power filter is proposed. This method has the advantages of using only one current sensor, a simple control circuit and low implementation cost. A model of this method is derived. A prototype is also developed to demonstrate the performance of this method. The test results show that the proposed active power filter has the expected performance View full abstract»

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  • Calculation and measurement of unbalanced magnetic pull in cage induction motors with eccentric rotors. I. Analytical model

    Publication Year: 1996 , Page(s): 193 - 201
    Cited by:  Papers (38)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (836 KB)  

    The paper describes an analytical model for cage induction motors with a static eccentric rotor. The method is based on an airgap permeance approach including stator and rotor MMF harmonics. The stator windings are resolved into harmonic conductor density distributions that allow different series/parallel winding connections to be accommodated in a straightforward manner. Sinusoidal and homopolar airgap field components are identified and the total airgap field distribution is used to determine the radial forces on the rotor. The model examines the principal harmonic interactions that influence the unbalanced magnetic pull View full abstract»

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  • Experimental study of the vibrational behaviour of machine stators

    Publication Year: 1996 , Page(s): 242 - 250
    Cited by:  Papers (7)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    In many applications the noise generated by electrical motors can be a significant factor in the overall design. Commercial applications such as locomotives or cruise liners and military applications such as antisubmarine frigates put particular emphasis on noise and vibration levels. The calculation of these levels involves an understanding of the electrical/mechanical interaction of magnetic force and stator behaviour. Analysis of the vibration behaviour of electrical machines has, in the past, concentrated on identifying the natural frequencies and mode shapes of highly symmetrical machine stators, for example stators of small motors. In practice, however, it has been found that geometrical and constructional irregularities introduce asymmetrical behaviour, which results in an enriched frequency response spectrum. The paper describes the results of modal tests carried out on an induction motor stator, and discusses the effects of irregularities on the vibration response of the machine. Based on the experimental investigation, some new and useful conclusions are derived. The implications for machine design are also discussed View full abstract»

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  • Performance of FFT-rotor slot harmonic speed detector for sensorless induction motor drives

    Publication Year: 1996 , Page(s): 258 - 268
    Cited by:  Papers (22)  |  Patents (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1016 KB)  

    The paper presents new results relating to real-time speed measurements obtained from the spectral estimation of rotor slot harmonic frequencies present in the stator currents of a cage induction motor. Derivations of the measurement accuracy and a method for attaining the maximum accuracy are presented. The paper derives expressions for predicting the performance under low motor loads and derives the region of signal indeterminacy in the torque-speed plane arising from interference by PWM harmonics. Tracking algorithms to reduce this indeterminacy are presented. A real time experimental implementation allows investigation of dynamic behaviour under speed transients. Use of the detector in speed controllers, and in particular, sensorless vector controllers, is discussed. The research forms part of a larger programme aimed at achieving field-oriented control performance from induction motor drives without a mechanical sensor View full abstract»

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  • New scheme of sliding-mode control for high performance induction motor drives

    Publication Year: 1996 , Page(s): 177 - 185
    Cited by:  Papers (10)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (708 KB)  

    A new sliding mode control approach for induction motor drives is presented. The control algorithm is based on the model of an induction motor in a frame rotating synchronously with the stator current vector. As with the indirect vector control of the induction motor, the method allows rotor flux and torque to be controlled by two independent control variables. The distinct advantage of the proposed method lies in its insensitivity to motor parameter variations. Since the control law is represented in a set of inequalities instead of equalities, as the motor parameters change, the stability of the sliding mode and the feature of independent control of the flux and torque will not be destroyed as long as the corresponding inequalities hold. Experiment results have verified the advantages of the method View full abstract»

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  • Robust speed-controlled induction-motor drive using EKF and RLS estimators

    Publication Year: 1996 , Page(s): 186 - 192
    Cited by:  Papers (23)  |  Patents (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (560 KB)  

    An induction-motor (IM) speed drive, with the application of an extended Kalman filter (EKF) and a proposed recursive least-square (RLS) estimator, is introduced. The rotor resistance of the IM is identified by the EKF, and the rotor inertia constant, the damping constant and the disturbed load torque of the IM are estimated by the proposed RLS estimator, which is composed of an RLS estimator and a torque observer. The integral proportional speed controller is on-line, designed according to the estimated rotor parameters. Then the observed disturbance torque is fed forward to increase the robustness of the induction-motor speed drive View full abstract»

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  • Damping the power-angle oscillations of a permanent-magnet synchronous generator with particular reference to wind turbine applications

    Publication Year: 1996 , Page(s): 269 - 280
    Cited by:  Papers (30)  |  Patents (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1016 KB)  

    The paper describes the use of a novel permanent-magnet synchronous generator for use with a wind turbine. The small pole pitch of the generator allows it to operate at low speeds, be directly coupled to the wind turbine and maintain a direct electrical grid connection. The ability to couple the generator directly to the wind turbine eliminates the need for the usual gearbox, but leads to a generator design where conventional damper windings are ineffective as there is too little space. The paper describes an alternative damping system whereby the stator is allowed limited rotational movement by connecting it to the wind turbine housing via a spring and a mechanical damper. This arrangement allows greater damping of power-angle oscillations than is possible using conventional damper windings. The response of the generator to step changes in driving torque is used to illustrate the effectiveness of such a design. The behaviour of the generator on both synchronisation and during operation in a varying wind is discussed to demonstrate the feasibility of this new design View full abstract»

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  • Doubly fed induction generator using back-to-back PWM converters and its application to variable-speed wind-energy generation

    Publication Year: 1996 , Page(s): 231 - 241
    Cited by:  Papers (633)  |  Patents (6)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (896 KB)  

    The paper describes the engineering and design of a doubly fed induction generator (DFIG), using back-to-back PWM voltage-source converters in the rotor circuit. A vector-control scheme for the supply-side PWM converter results in independent control of active and reactive power drawn the supply, while ensuring sinusoidal supply currents. Vector control of the rotor-connected converter provides for wide speed-range operation; the vector scheme is embedded in control loops which enable optimal speed tracking for maximum energy capture from the wind. An experimental rig, which represents a 7.5 kW variable speed wind-energy generation system is described, and experimental results are given that illustrate the excellent performance characteristics of the system. The paper considers a grid-connected system; a further paper will describe a stand-alone system View full abstract»

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  • Compound matrix partitioning and modification for the solution of branched autotransformer traction feeds

    Publication Year: 1996 , Page(s): 251 - 257
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (568 KB)  

    The increasing use of autotransformer feed schemes in AC electrified railways, as a result of their obvious advantages, motivates a detailed analysis of the behaviour of these systems. A novel compound matrix partitioning and modification method for the solution of a branched autotransformer feed system is presented. The introduction of branch lines in the autotransformer feed model has stimulated the development of a new solution technique which is very well matched to the problem formation. Results are cited which indicate that the proposed method can achieve a very efficient and reliable solution View full abstract»

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  • Loss-of-mains detection for small generators

    Publication Year: 1996 , Page(s): 225 - 230
    Cited by:  Papers (16)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (512 KB)  

    A new loss-of-mains detection method for use with very small generators is proposed. A known load is repeatedly switched on to the supply, and the resulting voltage changes used to estimate the source impedance, and hence to detect loss of mains. Correlating the load switching with the voltage change prevents false operation arising from random load changes. Experiments and simulations are discussed which demonstrate the principles of the technique. Test results are presented which show that the technique operates correctly, and can reliably detect a loss of mains without being susceptible to false tripping View full abstract»

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