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The simultaneous elimination of common-mode voltage and DC-link capacitor voltage imbalance is achieved in a five-level inverter scheme for an induction motor drive throughout its operating range. A dual five-level inverter-fed open-end-winding induction motor structure is used for the proposed drive. Initially, the operating limitations of achieving this dual task for the five-level inverter configuration are investigated for a single DC power supply. Subsequently, a switching strategy for a five-level inverter topology with two DC power supplies is proposed to achieve the dual task over the entire speed range of the drive. The proposed drive offers a simple power-bus structure with more redundant switching combinations for inverter voltage vectors, and requires a lower voltage-blocking capacity of the power devices as compared with the conventional single five-level inverter-fed drive. As only the availability of redundant switching combinations for inverter voltage vectors is exploited, the dual task is achieved without disturbing the fundamental component of the inverter output voltage and the scheme does not need any extra control circuit hardware. Experimental verification of the proposed scheme is done on a 1.5 kW induction motor drive in the linear as well as overmodulation range. [ABSTRACT FROM AUTHOR]

The movement of a linear induction motor (LIM) causes eddy currents in the secondary conductor sheet at the entry and the exit of the primary core. The eddy currents of the sheet tend to resist sudden flux variation, allowing only gradual change along the airgap. Hence, the so-called ‘end effect’ causes not only the losses but also airgap flux profile variation changes depending on the speed. In this work, an equivalent circuit model of LIM is developed following Duncan's per phase model. It is then transformed into a synchronous reference frame which is aligned with the secondary flux. Also, a field orientation control scheme is developed which accounts for the end effect. The validity of the proposed LIM model is demonstrated by comparing experimental and simulated voltage current relations. With the proposed control scheme, the (secondary) flux-attenuation problem due to the end effect is shown to be resolved in the high-speed range. [ABSTRACT FROM AUTHOR]

An adaptive fuzzy total-sliding-mode controller (AFTSMC) with a total switching surface is proposed to control the position of an electrical servodrive. The proposed controller comprises a special fuzzy total-sliding-mode controller (FTSMC) and an adaptive tuner. The FTSMC acts as the main tracking controller, which is designed via a fuzzy system to mimic the merits of a total-sliding-mode controller (TSMC). In addition, a translation width is embedded into fuzzy rules to reduce the chattering phenomena. The adaptive tuner, which is derived in the sense of Lyapunov stability theorem, is utilised to adjust the translation width on-line for further assuring robust and optimal performance. In the AFTSMC, the fuzzy-control-rules base is compact and only one parameter needs to be adjusted. An electrical servodrive with the proposed position-control system possesses the advantages of a simple control framework, reduced chattering, stable performance and robustness to uncertainties. The effectiveness is demonstrated by simulated and experimental results, and its advantages are indicated in comparison with conventional TSMC and adaptive TSMC for a field-oriented control induction-motor (IM) drive. [ABSTRACT FROM AUTHOR]

Most induction motor analyses that allow for the presence of inter-bar currents are based on a rotor model in which the inter-bar currents are assumed to flow between adjacent pairs of bars. An alternative model is proposed in which the inter-bar currents flow into and around the rotor core. The validity of the new model is verified by means of measurements made on 54 rotors of identical design, which have been subjected to a range of treatments during manufacture to produce bar-to-bar resistances that differ by up to three orders of magnitude. It is shown that the new rotor model may readily be incorporated into existing analyses by redefining a single inter-bar resistance parameter. An alternative viewpoint of this is that the new rotor model redefines the relationship between the resistance parameter used in analytical models and the bar-to-bar resistance measured under test. [ABSTRACT FROM AUTHOR]

The paper addresses the bearingless induction motor based on the concept of dual-pole windings, one controlling the motor torque and the other the generated radial forces. Such machines have been investigated experimentally in the past. The paper presents a simulation model capable of investigating the effect of induction-machine design on the generation and control of the radial force. The simulation is based on the dynamic reluctance-mesh field model embedded in vector control systems for the decoupled control of torque, flux and radial force. In the paper, the rotor is constrained by a mechanical bearing so that the radial force is used to cancel the rotor weight to effect 'bearing relief'. The paper summarises the modelling method, investigates the radial force production in both cage and wound rotor machines, and introduces a mixed field orientation method for the decoupled control of the torque and radial forces. Simulations are undertaken showing good generation of radial force under zero speed, acceleration and transient load conditions. [ABSTRACT FROM AUTHOR]

The speed control of a field-weakened (FW) indirect field-oriented (IFO) induction motor drive with compensations for system dead-time and parameter variations is presented. Firstly, the DSP-based motor drive with a field-weakening mechanism is designed. To handle the command tracking and load rejection speed controls simultaneously, the proposed control scheme consists of a feedback controller and a command feedforward controller (FC) to possess two degrees of freedom (2DOF). The feedback controller is designed according to the given load rejection control requirements, and the command FC is set as the inverse plant model to let the tracking response follow the one defined by a reference model. Then, to reduce the effects of system dead-time and parameter variations on the speed control performance, a dead-time and disturbance compensator (DTDC) is proposed with its parameters being adapted by a variable-structure system (VSS). In addition to dead-time compensation, an estimated signal containing plant uncertainties and disturbances is generated and used for cancelling their effects on dead-time compensation control. Moreover, the tracking response is further enhanced by adaptively adjusting the parameters set in the FC and the DTDC according to the estimated mechanical inertia change. The practical considerations for simultaneously providing a good load rejection control response are also presented. Finally, the closed-loop regulation control is provided by adding a linear model following control (LMFC) scheme. [ABSTRACT FROM AUTHOR]