Nesimi Ertugrul

Field-weakening performance of interior permanent-magnet motors

This paper compares the field-weakening performance under rated and overload conditions of synchronous reluctance and interior permanent-magnet motors against that of a baseline 2.2-kW induction machine. Four prototype rotors based on axially laminated and multiple-barrier designs were built and tested in the same induction machine stator. Field-weakening performance was estimated based on 50-Hz load tests at reduced voltage. It was found that the performance of the axially laminated synchronous reluctance machine was comparable with the induction machine while the interior permanent-magnet motors offered significantly better output power above rated speed. The multiple-barrier interior permanent-magnet motor design gave the most promising field-weakening performance.

Fault tolerant motor drive system with redundancy for critical applications

Some of the recent research activities in the area of electric motor drives for critical applications (such as aerospace and nuclear power plants) are focused on looking at various motor and drive topologies. This paper presents a motor drive system, which provides an inverter topology for three-phase motors, and also proposes an increased redundancy. The paper develops a simulation model for the complete drive system including synthetic faults. In addition, the hardware details including the implementation of DSP based motor controller, inverter module, and brushless PM motor system are provided and some experimental results are presented.

Automatic Classification and Characterization of Power Quality Events

This paper presents a new technique for automatic monitoring of power quality events, which is based on the multiresolution S-transform and Parsevals theorem. In the proposed technique, the S-transform is used to produce instantaneous frequency vectors of the signals, and then the energies of these vectors, based on the Parsevals theorem, are utilized for automatically monitoring and classification of power quality events. The advantage of the proposed algorithm is its ability to distinguish different power quality classes easily. In addition, the magnitude, duration, and frequency content of the disturbances can be accurately identified in order to characterize the disturbances. The paper provides the theoretical background of the technique and presents a wide range of analyses to demonstrate its effectiveness.

High robustness and reliability of fuzzy logic based position estimation for sensorless switched reluctance motor drives

In many applications where motor drives are used, concern. Thus, a major consideration is the reliability of position estimation schemes when sensor less SR motor drive control is employed. Hence, in this paper, the robust of a fuzzy logic based angle estimation algorithm for the switched reluctance motor (SR) motor is described. It is shown using theoretical analysis and experimental results, that by using logic, the angle estimation scheme gains a high level of robustness and reliability. A theoretical and quantitative analysis of the noise and error commonly found in practical motor drives is given, and how this can affect SR motor position estimation. An analysis is also given on the concepts of robustness and reliability. It is shown that the fuzzy logic based scheme is robust to erroneous and noisy signals commonly found in motor drives.

Investigation of Effective Automatic Recognition Systems of Power-Quality Events

There is a need to analyze power-quality (PQ) signals and to extract their distinctive features to take preventative actions in power systems. This paper offers an effective solution to automatically classify PQ signals using Hilbert and Clarke Transforms as new feature extraction techniques. Both techniques accommodate Nearest Neighbor Technique for automatic recognition of PQ events. The Hilbert transform is introduced as single-phase monitoring technique, while with the Clarke Transformation all the three-phases can be monitored simultaneously. The performance of each technique is compared with the most recent techniques (S-Transform and Wavelet Transform) using an extensive number of simulated PQ events that are divided into nine classes. In addition, the paper investigates the optimum selection of number of neighbors to minimize the classification errors in Nearest Neighbor Technique.

Use of fuzzy logic for modeling, estimation, and prediction in switched reluctance motor drives

Switched reluctance motor drives may be used in many commercial applications due to their simplicity and low cost. These drives require rotor position feedback to operate. However, in many systems, rotor position sensors have disadvantages. In this paper, a position sensorless scheme is described which uses fuzzy modeling, estimation and prediction. An important feature is that saturation and real-time nonideal effects are not ignored, but that no mathematical model is required. Instead, a fuzzy logic-based model is constructed from both static and real-time motor data, and from this model the rotor position is estimated. The system also incorporates fuzzy logic-based methods to provide a high robustness against noise. This includes a fuzzy predictive filter which combines both fuzzy logic-based time-series prediction, as well as a heuristic knowledge-based algorithm to detect and discard feedback signal error. In addition, the method uses heuristic knowledge to choose the most desirable phase for angle estimation in order to minimize the effect of feedback error. It is also shown that, by using fuzzy logic, the estimation scheme offers a high robustness and reliability and is thus well suited to a wide range of systems.

Computer-based automated test measurement system for determining magnetization characteristics of switched reluctance motors

This paper describes a fully automated method of measuring the magnetization characteristics (flux linkage versus current and position) of switched-reluctance (SR) motors. The measuring scheme was developed using a graphical programming environment (LabVIEW), a data acquisition card, and external interface hardware. The graphical programming method allows a high degree of software modularity and provides the features needed fur sensor zero adjustment, data acquisition and analysis, and automated presentation of results. Furthermore, the experimental setup described in this paper can be used to obtain the magnetization characteristics of other electromechanical devices. Experimentally measured results from a test SR motor using the scheme are presented in the paper.

Iron Loss Reduction in an Interior PM Automotive Alternator

This paper examines the iron loss characteristics of a high-flux interior permanent-magnet machine. The machine was designed as a concept demonstrator for a 6-kW automotive alternator and has a wide field-weakening range. Initial experimental results revealed a high iron loss during field-weakening operation. Finite-element analysis was used to investigate the cause of the high iron losses and to predict their magnitude as a function of speed. The effects of changes in the machine design were examined in order to reduce iron losses and hence improve the machine performance

Indirect angle estimation in switched reluctance motor drive using fuzzy logic based motor model

In this paper, a novel rotor position estimation scheme is described that was developed to overcome the drawbacks of the previous sensorless techniques, which were proposed for switched reluctance (SR) motor drives. It is based on fuzzy-logic, and does not require complex mathematical models or large look up tables. The scheme was implemented by using a digital signal processor. The real-time experimental results given in this paper show that the position estimation method proposed can provide accurate and continual position data over a wide range of speeds (zero/low/high), and can also function accurately at different operating conditions (chopping/single pulse mode and steady state/transient operation).

Investigation of switched-mode rectifier for control of small-scale wind turbines

This paper investigates the suitability and experimental testing of a simple power converter for a permanent magnet generator for use with a small-scale variable-speed wind turbine. The controller uses a switched-mode rectifier in conjunction with a high inductance generator that allows generator torque and power to be controlled via the switch duty-cycle. The controller maximises output power for wind speeds below rated, and limits turbine speed for higher wind speeds. Dynamometer and limited wind turbine test results are presented.