C. De Angelo

Online Model-Based Stator-Fault Detection and Identification in Induction Motors

In this paper, a model-based strategy for stator-interturn short-circuit detection on induction motors is presented. The proposed strategy is based on the generation of a vector of specific residual using a state observer. The vectorial residual is generated from a decomposition of the current estimation error. This allows for a fast detection of incipient faults, independently of the phase in which the fault occurs. Since the observer includes an adaptive scheme for rotor-speed estimation, the proposed scheme can be implemented for online monitoring, by measuring only stator voltages and currents. It is shown that the proposed strategy presents very low sensitivity to load variations and power-supply perturbations. Experimental results are included to show the ability of the proposed strategy for detecting incipient faults, including a low number of short-circuited turns and low fault current.

A 2-D model of the induction machine: an extension of the modified winding function approach

A new method to calculate the inductances of induction machines considering axial nonuniformity is proposed. The proposed method, an extension of the modified winding function approach, allows considering nonuniformity due to skew and static and dynamic air-gap eccentricity. Theoretical fundamentals and experimental results that validate the proposed method are presented.

Separating Broken Rotor Bars and Load Oscillations on IM Fault Diagnosis Through the Instantaneous Active and Reactive Currents

A new method for broken rotor bars and load oscillation diagnosis on induction motors is presented. The proposed strategy is based on the decomposition of the stator currents into their instantaneous active and reactive current components. Such components allow the decoupling of the effects produced by rotor asymmetries from those produced by oscillating loads. This allows not only the proper fault detection but also a correct fault diagnosis. Simulation and experimental results, both from laboratory and industrial cases, are presented to validate the proposal.

Maximization of the Traction Forces in a 2WD Electric Vehicle

A new control strategy for obtaining the maximum traction force of electric vehicles with individual rear-wheel drive is presented. A sliding-mode observer is proposed to estimate the wheel slip and vehicle velocity under unknown road conditions by measuring only the wheel speeds. The proposed observer is based on the LuGre dynamic friction model and allows the maximum transmissible torque for each driven wheel to be obtained instantaneously. The maximum torque can be determined at any operating point and road condition, thus avoiding wheel skid. The proposed strategy maximizes the traction force while avoiding tire skid by controlling the torque of each traction motor. Simulation results using a complete vehicle model under different road conditions are presented to validate the proposed strategy.

Mechanical sensorless speed control of permanent-magnet AC motors driving an unknown load

A new sensorless scheme for high-performance speed control of permanent-magnet ac motors (PMACMs) driving an unknown load is proposed. This scheme uses an extended nonlinear reduced-order observer to estimate the induced electromotive force (EMF) and load torque. From the estimated variables, the rotor position, the rotor speed, and the position derivative of flux are calculated and are used to close the control loop. In order to improve the drive performance, the estimated load torque is incorporated as a feedforward signal in the closed control loop. In addition, the proposed sensorless PMACM drive allows the torque-ripple and copper-loss minimization for motors with an arbitrary EMF waveform. Simulation and experimental results to validate the proposal are presented in this paper.

Application of an Additional Excitation in Inverter-Fed Induction Motors for Air-Gap Eccentricity Diagnosis

In this paper, the application of an additional excitation in induction motor (IM) drives for static, dynamic, and mixed eccentricity diagnosis is proposed. The additional excitation consists in a predefined inverter-switching pattern that is applied on the motor for a short time, while the fundamental excitation is canceled. This excitation was used previously to implement a position estimation strategy. The strategy obtains information about the rotor position from the motor saliencies effects over the zero-sequence voltage. The air-gap eccentricity is a kind of saliency that affects the zero-sequence voltage and allows the use of the additional excitation for eccentricity diagnosis. For the evaluation of the feasibility of this proposal, a multiple-coupled circuit model of the IM is used. The effects of series and series-parallel stator winding connections on the diagnosis signals are shown. Experimental results to validate the proposal are also given. These results show that it is possible to use the diagnosis strategy in a self-commissioning scheme

A rotor position and speed observer for permanent-magnet motors with nonsinusoidal EMF waveform

A new nonlinear reduced-order observer to estimate the rotor speed and position for permanent-magnet motors, with arbitrary electromotive force (EMF) waveform, is presented. The proposed observer is suitable for the realization of a torque control with minimum torque ripple. In order to implement the observer, the EMF generated by the motor is first obtained experimentally offline. After that, it is approximated by a Fourier series in order to develop the model to be used in the online estimation. From the estimated EMF, rotor position and speed are calculated using the relationship between the EMF and the rotor variables. The proposal is validated with experimental results.

A 2D-model of the induction motor: an extension of the modified winding function approach

In this paper, a method to calculate the inductances of an induction machine with axial nonuniformity is presented. The analyzed axial nonuniformities are skew and rotor eccentricities. The inductance calculation is based on an extension of the modified winding function approach. Theoretical fundaments of this extension are presented. The coupled magnetic circuits approach has been used for modeling the induction machine. Experimental results that validate the proposal are also presented.

Effects of rotor bar and end-ring faults over the signals of a position estimation strategy for induction motors

The effect of rotor faults, such as broken bars and end rings, over the signals of a position estimation strategy for induction motor drives is analyzed using a multiple coupled circuit model. The objective is to establish the possibility of using the estimation strategy signals for fault diagnosis in variable speed electric drives. This strategy is based on the effect produced by inductance variation on the zero sequence voltage, exciting the motor with a predefined inverter-switching pattern. Experimental results illustrate the feasibility of the proposal.

Evaluation of harmonic current sidebands for broken bar diagnosis in induction motors

Effects of rotor faults on stator currents in induction motors are studied in the present work. Particularly, the effects of such faults on the sidebands at fundamental and harmonics current components are analyzed. A multiple-coupled circuit model determines the variation of amplitude of these sidebands as a function of the number of broken bars, load and motor-load inertia. The results obtained from this analysis allow improving the rotor fault diagnosis techniques and identifying and separating rotor faults from others. Simulation and experimental results are presented to validate the proposal.