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The supply-side current of an inverter-fed induction motor (IM) is easily accessible and less affected by noises than the motor stator current. This paper proposes a novel sensorless speed estimation method for an IM using the spectrum of the supply-side current. However, due to the influence of fundamental supply frequency, it is difficult to carry out the speed detection straight from the supply-side current signal. In this paper, an analytic model for characterizing the supply-side current of an inverter-fed IM using the modulation theory and the switching function concept is developed. Then, the Hilbert transform is applied to extract the speed harmonic component from the supply-side current. Finally, an interpolated Goertzel algorithm is put forward to enhance the estimation precision of IM speed. The performance of the proposed sensorless speed estimation method is proved by the speed estimation results obtained from hardware experiments of an IM fed by an inverter under different load conditions. [ABSTRACT FROM AUTHOR]

In this paper, a multilevel inverter based on three-phase H-bridge inverters for an open-end winding induction motor drive is presented and its fault-tolerance capability is investigated. The multilevel topology is obtained using three wye-connected three-phase H-bridge inverters to supply open-end winding induction motors. This topology has the ability to extend the maximum voltage applied to the motor windings up to two times the dc supply voltage of the three-phase inverters. For a given induction motor voltage, the topology allows the use of dc sources with a lower voltage rating. Consequently, faster power semiconductors can be used. This multilevel topology can be directly controlled by modifying known modulation concepts, such as sinusoidal pulse width modulation (PWM). In this study, two sinusoidal PWM modulation techniques will be implemented: the level-shifted carriers (phase disposition) and the phase-shifted modulator. Fault-tolerant operation under an open-switch fault without adding any extra components and without changing the modulation strategy is also proposed, adding fault-tolerant capability to the new topology. Experimental results of this multilevel inverter in normal operation and in fault tolerant mode are presented. The obtained results confirm the fault effectiveness of the proposed multilevel topology. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a new method for an online electric parameters identification of an induction motor (IM). This method is carried out in the IM standstill configuration and uses adaptive linear neuron (ADALINE) networks. In order to simplify the identification process, the IM model is approximated by two first-order subsystems: one is valid at low frequencies (LFs), called the slow system and the other is valid at high frequencies (HFs), called the fast system. By means of two ADALINE networks, the parameters of the slow system and the fast system are identified in LFs and HFs, respectively, and thus, the required IM parameters are derived. Finally, experimental results are presented in order to validate the proposed method and to check the accuracy of the obtained parameters. The originality of this paper is the building of a model representation that is suitable for implementation with ADALINE networks. This leads to a simple implementation and ease of parameters identification. [ABSTRACT FROM AUTHOR]

This paper investigates the opportunity for energy saving in a three-phase induction motor (IM) driving pump load and proposes an improved loss model control (LMC). Compared with other power-loss reduction algorithms for IM, the presented one has the advantages of fast and smooth flux adaptation, high accuracy, and versatile implementation. The performance of LMC depends mainly on the accuracy of modeling the motor drive and losses. In this paper, the derived loss model considers the surplus power loss caused by inverter voltage harmonics using closed-form equations and also includes the magnetic saturation. An artificial neural network controller is synthesized and trained offline to determine the optimal flux level that achieves maximum drive efficiency. The drive's voltage and speed control loops are connected via the actual stator frequency, making the scheme comparatively reliable. Simulation and experimental studies are performed on 5.5-kW test motor using the proposed control method. The test results are provided and compared with the fixed flux operation to validate the effectiveness. [ABSTRACT FROM PUBLISHER]

In the last decade, the use of PWM voltage-source inverters to control three-phase squirrel-cage induction motors has increased significantly. Consequently, high-frequency current activity in the bearings of inverter-fed motors and/or of devices mechanically coupled to their shaft is presently a common issue, ultimately shortening the bearings lifetime. In fact, bearing failures occurrence in inverter-fed motors increased dramatically in the last few years. Recently, the effectiveness of insulation-based bearing current mitigation techniques (e.g., bearings with insulated rings or ceramic spheres) and/or motor shaft grounding with an electric contact brush has been fairly investigated. However, there are some alternative high-frequency common-mode bearing current mitigation techniques requiring further investigation. In this paper, a stator slot-embedded partial electrostatic shield to reduce the capacitive coupling between the stator windings and the rotor in inverter-fed motors is proposed, analyzed, and implemented, being experimentally demonstrated its practicability and effectiveness in attenuating the common-mode voltage between the rotor shaft and the frame/ground, contributing to the reduction of high-frequency common-mode bearing current activity. [ABSTRACT FROM PUBLISHER]