G. R. Bossio

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.

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.

Experimental generation and quantification of stator core faults on induction motors

A non-destructive method to analyze stator core faults on induction motors is presented and developed in the present work. It allows generating entirely reversible faults of different magnitudes. The quantification of fault severity was performed through the stator core interlaminar insulation test and through no-load test. The obtained experimental results show the feasibility of the method and the detectability of generated faults, which makes it a useful method to develop new diagnosis strategies.

Speed control of PMSMs with Interconnection and Damping Assignment or Feedback Linearization. Comments about their performance

The performance of interconnection and damping assignment strategy applied to speed control of permanent magnet synchronous motors is analyzed. It is noted that closed loop performance depends on interconnection and damping values injected by the controller. Certain designs produce nonlinear and coupled dynamics. When it is the case, the motor performance is degraded since direct current loop is adversely affected by the speed one. Then, from the nominal performance point of view some selections behave better than other ones. It is demonstrated that interconnection and damping assignment degrees of freedom can be used for improving the nominal performance. Interconnection assignment is calculated for constructing speed and direct current decoupled loops. In this case, tracking error dynamics becomes linear and its convergence speed can be adjusted by using the injected damping. Additionally, it is established that interconnection and damping assignment strategy attaining two decoupled tracking error dynamics loops results in feedback linearization.

Stator core fault diagnosis for induction motors based on parameters adaptation

A novel on-line stator core fault diagnosis method for Induction Motors (IM) is proposed. This approach is based on an adaptive state observer; it is derived from the IM dynamic model considering stator iron losses. In this model the iron losses are represented by an equivalent iron loss resistance (RFe). Stator core fault causes important variations on iron losses and these variations are reflected on the RFe. Therefore the proposed adaptive state observer estimates RFe with the objective of diagnosing stator core fault. Simulation and experimental results for different fault severity conditions are showed. These results demonstrated the validity of the method. In addition, simulation results proved that the proposal is not sensitive to load torque variations.

Sensorless speed control of permanent magnet motors driving an unknown load

A sensorless strategy for speed control of permanent motors driving an unknown load torque is presented. The proposed strategy uses an extended non-linear reduced-order observer that includes information about the waveform of the EMF generated by the motor, which is neither sinusoidal nor trapezoidal. In order to improve the drive performance, the unknown disturbance torque is estimated by means of an adaptive law, and is incorporated as feedforward signal into the control loop. It allows the realization of torque control avoiding position sensor and with minimum torque ripple. Simulation results that validate the proposal are shown.

Fault detection in magnetic wedges of induction motor

In high power electric motors it is common to use open slots to facilitate the assembly of the coils. Open slots introduce harmonics in the magnetomotive force distribution over the air gap, resulting in additional losses and parasitic torques. In order to reduce these effects, wedges of magnetic material are used. These wedges are prone to apartial or total detachment, which in turn may result in other failures. In this paper a strategy to detect faults in magnetic wedges is presented. This strategy consists of the injection of a zero sequence voltage signal of high frequency. The resulting currents are highly dependent on the magnetic irregularities both the rotor and stator and thus sensitive to asymmetries produced by faults in the wedges. In this way, it is possible to detect and quantify wedges faults without the need to disassemble or remove the IM from the production line. The proposed strategy is applicable offline and required only disconnect the motor of the power supply. Laboratory experimental results are presented to validate the proposal.

Integrated motors and controllers for 42 V automotive auxiliary motor applications

This work focuses on technical barriers to the implementation of controllers for auxiliary electric motors for automotive applications. It addresses the integration of three-phase brushless DC motors and advanced microelectronic packaging techniques into compact motor controllers. The proposed packaging techniques are focused on thermal performance utilizing minimum supplemental cooling. The primary focus of this discussion is the reduction of thermal resistance by the elimination of interfaces between the power devices and the heat sink. The initial application of this work is targeted at variable speed compressors for 42 V vehicles.