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Electric Power Applications, IEE Proceedings -

Issue 6 • Date Nov 1996

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Displaying Results 1 - 12 of 12
  • New inverter-driven design and control method for two-phase induction motor drives

    Page(s): 458 - 466
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (820 KB)  

    A simple inverter circuit is proposed for driving symmetrical and unsymmetrical two-phase induction motors. The inverter provides two-phase independently controlled variable-frequency variable voltages to the primary and auxiliary windings of an induction motor. The dynamic model of the two-phase induction motor driven by the inverter is established. An experimental prototype, which consists of a single-chip microprocessor-based controller, the inverter, and the motor and load, is constructed. Both computer simulation and experimental results show the effectiveness of the proposed inverter-driven motor in achieving higher performance, such as less torque and speed pulsation and reduced vibration and noise, than the conventional motors View full abstract»

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  • Performance and design optimisation of electric motors with heteropolar surface magnets and homopolar windings

    Page(s): 429 - 436
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (936 KB)  

    Electric motors that embody heteropolar arrays of rotor magnets interacting with homopolar stator windings are capable of exceptionally high levels of torque per unit volume or mass. Design studies of the surface-magnet form of this class of machine have determined optimum values for the following ratios: C-core pitch/gap, magnet depth/gap, and C-core width/C-core pitch. The results are presented partly in the paper, which concentrates on three-dimensional computational design studies and on physical discussion of behaviour, and partly in a companion paper, which concentrates on theory of performance and figures of merit for design View full abstract»

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  • Fault-tolerant permanent magnet machine drives

    Page(s): 437 - 442
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (600 KB)  

    The paper examines the use of permanent magnet machine drives in high performance, safety-critical applications. Likely fault modes are identified and machine designs are developed for fault-tolerant operation, without severely compromising the drive performance. Fault tolerance is achieved by adopting a modular approach to the drive, with each phase electrically, magnetically, thermally and physically independent of all others. Power converter requirements are discussed and methods for controlling a faulted phase developed to minimise the impact of a machine or power converter fault View full abstract»

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  • Discrete integral variable structure model following control for induction motor drivers

    Page(s): 467 - 474
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (608 KB)  

    A DSP microprocessor based high performance vector-controlled induction motor driver is presented. The discrete-time integral variable structure model following the control (DIVSMFC) approach is proposed for the outer loop of the driven system. A design procedure is developed for determining the control function, the switching plane and the integral control gain such that the error between the state of the model and the controlled plant is minimised. Simulation and experimental results show that the proposed scheme can achieve accurate position/velocity servo-tracking in the presence of load disturbances and plant parameter variations View full abstract»

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  • Representation of rotor spiders and axial ventilation ducts in reduced finite-element models for cage rotors

    Page(s): 423 - 428
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (508 KB)  

    The authors examine a number of alternative schemes for incorporating rotor asymmetries in reduced finite-element models of cage motor rotors. The asymmetries examined arise as a result of the use of spider arms to support the rotor core on the shaft or axial ventilation holes in the rotor core back. Calculated results show that both features can be allowed for with adequate accuracy in a model that spans a single-slot pitch View full abstract»

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  • Relationship between rated torque and size of permanent magnet machines

    Page(s): 417 - 422
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    The rated output of induction motors varies with frame size in a manner which is well known to designers of these machines. However, in the case of permanent magnet excited machines, there is a shortage of comparable information. The aim of the paper is to use both analysis and published results to attack this problem. The analysis is presented in terms of torque and the principal dimensions of rotor diameter and length for cylindrical machines. Results are tabulated for a range of machines with rare-earth magnets in terms of available torque output. A clear relationship involving magnet volume and rotor diameter is shown. Consideration of cooling of the stator leads to the conclusion that the observed relationship between torque and dimensions is important for maintaining a satisfactory frame temperature. The effect of the scaling factors on the capability of field weakening for high speed operation is also studied. The general scaling rule should prove useful in establishing the basic size of machine needed for a given output requirement View full abstract»

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  • Broken rotor bars: their effect on the transient performance of induction machines

    Page(s): 449 - 457
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (924 KB)  

    Around 10% of failures in cage induction motors are on the rotor. Problems result from defective castings in die-cast rotors, or from high resistance joints as a result of poor welding or brazing in fabricated cages. In such cases uneven bar stress is then unavoidable. Often, however, failure occurs due to fracture of bars caused by fatigue. This is common in machines with uneven and heavy duty cycles, which consequently are subject to high stress in the cage during periods of rapid braking and acceleration. Some success has been achieved in the development of techniques to identify bar failure, or high resistance joints, even on operational machines. The majority of techniques depend upon detecting a twice-slip frequency modulation in speed, torque or stator current by analysing an appropriate frequency spectrum. As yet, there is still no universally effective procedure for the early detection of such conditions. In this contribution, rotor parameters are evaluated allowing for current redistribution in the damaged rotor cage, and for the concomitant changes in resistance which result. Based upon this, a modified model of the induction machine, which includes the effect of broken rotor bars, and which will represent both transient and steady state behaviour, is developed. Experimental and calculated results compare the transient performance of the healthy and faulty machines View full abstract»

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  • Improved design for electric vehicle induction motors using an optimisation procedure

    Page(s): 410 - 416
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    A design technique for electric vehicle (EV) induction motors using an optimisation procedure is described. The supply inverter operates in PWM mode with a field orientated controller in both the constant torque and the constant power regions. The motor voltage regulation strategies are discussed in the first part of the paper, because the motor design and the inverter kVA size are related to it. Thus, the nonlinear programming technique is applied for the three-phase induction motors designs in the design procedure. The proposed method has been applied to design a 17.5 kW induction motor with 30 kW maximum power. Complete design results for motors with different characteristics (voltage regulation strategy, pole number, base and maximum speeds) are presented and discussed View full abstract»

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  • Slotless-armature DC drives for surface warship propulsion

    Page(s): 443 - 448
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (604 KB)  

    A slotless armature with multiplex connection can operate with higher coil voltage and current than a conventional armature before the commutation limits are reached and so can achieve higher power ratings. DC motors may thus be designed for powers of tens of MW, suitable for direct-drive ship propulsion. The field system may use conventional wound poles, permanent magnets or superconducting coils for excitation. Slotless-armature designs using alternative types of field system are compared with a conventional slotted design for 10 MW, 150 rev/min rating. The slotless-armature superconducting-field design offers the lightest and most compact overall arrangement and the best full-load efficiency. However, permanent-magnet excitation offers a much simpler solution, is the cheapest to build and gives better part-load efficiency. A more detailed design for a 15 MW, 200 rev/min permanent-magnet ship propulsion machine is presented View full abstract»

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  • Current sensorless field-oriented control of induction motors

    Page(s): 492 - 500
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (796 KB)  

    A new method for controlling a current sensorless induction motor is presented. It uses a partial state estimator to estimate the torque-current and a voltage predictor to predict the voltage vector of a voltage source inverter (VSI). In the system, a speed controller, a torque-current estimator, a voltage-predictive voltage-source inverter (VPVSI) and a slip calculator are included. Fast response and adaptive field weakening above the base speed of the induction motor are achieved through a direct software control system based on field orientation with recursive operation between partial state estimation and voltage prediction. Besides low cost, the simplicity of the system hardware yields high reliability and good maintainability View full abstract»

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  • Solid-state on-load transformer tap changer

    Page(s): 481 - 491
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (896 KB)  

    Switching logic is defined for a single-phase transformer tap changer using thyristor switching. A laboratory model validates the theory and shows that tap changing is possible in less than one cycle over the whole power-factor spectrum. Waveform sampling and the use of a microprocessor based control system provides improved control and additional features such as data logging etc. Two schemes are considered for the application of thyristor tap changing to three-phase transformers. Economic viability is strongly dependent on the associated power system and its abnormal operating features, namely system fault currents and especially the degree of exposure of the transformer to lightning surges View full abstract»

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  • IGBT based zero voltage transition full bridge PWM converter for high power applications

    Page(s): 475 - 480
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (500 KB)  

    A novel zero-voltage-transition (ZVT) full-bridge (FB) PWM converter for high power applications is proposed. An auxiliary resonant network which consists of two small switches (10-20% of main switches) and one small inductor provides zero-voltage-switching (ZVS) for wide line and load ranges. This allows addition of external capacitors to the switches maintaining reasonable ZVS range, and IGBTs can be used instead of MOSFETs for the main switches. In addition, the proposed converter has advantages over the ZVS-FB-PWM converters such as minimum device voltage and current stresses, negligible duty cycle loss, and no severe parasitic ringing on the secondary, which enables the proposed converter to handle higher voltage and power with lower cost. Operation, features and design considerations are presented and verified experimentally on a 2 kW, 85 kHz IGBT based prototype View full abstract»

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