Ali Sarikhani

Inter-Turn Fault Detection in PM Synchronous Machines by Physics-Based Back Electromotive Force Estimation

In this paper, the inter-turn short circuit fault detection in permanent magnet synchronous machines (PMSM) using an open-loop physics-based back electromotive force (EMF) estimator is presented. The back EMF estimator is designed based upon a current mode tracking scheme. The thermal and saturation aspects of the machine are considered in the design of the estimator. The design procedure and stability criteria of the estimator are presented in detail. The fault detection is carried out based on the difference between the estimated back EMF and a reference back EMF. A 0.8 (kW) PMSM is studied experimentally as well as numerically under different inter-turn fault and operational contingencies. The numerical modeling is accomplished by a finite-element-based model coupled with the thermal network and polluted with inter-turn fault. The acceptable agreement between the simulated and experimental result validates the modeling process. The back EMF estimator fault detection system is led to discriminative inter-turn fault signatures in a fraction of second for wide speed range even in the presence of harmonic loads and dynamic eccentricities.

Evaluation of radiated Electromagnetic Field Interference due to frequency switching in PWM motor drives by 3D finite elements

This paper investigates the effect of switching frequency of PWM motor drives on radiated Electromagnetic Field Interference (EMI). The excitation system for the radiated EMI evaluations consists of a high frequency PM machine model, a high frequency cable model, and a low frequency IGBT drive model. This system provides us with the conducted EMI currents through ground paths. The radiated EMI is modeled as a time harmonic electromagnetic wave which is propagated through all the components of the electric drive system. The Radiated EMI were evaluated by 3DFE analysis, using COMSOL multiphysics, with the conducted EMI currents as the supply source of the radiated fields. The results of the proposed 3DFE model follow expected patterns and provide a novel numerical alternative during the design and development stage of electric motor drive systems.This paper investigates the effect of the switching frequency of pulse width modulation (PWM) motor drives on radiated Electromagnetic Field Interference (EMI) due to common Mode (CM) ground currents. A technique with two successive steps is used to simulate conducted as well as the radiated EMI. At first, a high-frequency permanent magnet (PM) machine model, a high-frequency cable model, and a low-frequency IGBT drive model are employed to simulate the common mode (CM) current through ground paths, conducted EMI. The radiated EMI is modeled as a time harmonic electromagnetic wave which is propagated through all the components of the electric drive system. The Radiated EMI were evaluated by 3DFE analysis while the simulated common mode (CM) ground current from the first step was used as the supply source of the radiated fields. The results of this two step technique follow the expected patterns and provides a novel numerical alternative during the design and development stage of electric motor drive systems.

Demagnetization Control for Reliable Flux Weakening Control in PM Synchronous Machine

A process for permanent magnet (PM) demagnetization control for optimal and reliable flux weakening control in permanent magnet synchronous machines (PMSM) is presented. A physics-based model was developed to estimate the magnetic flux operating point of the PM poles during the operation of PMSM. The model is enabled to dynamically estimate the average and the partial PM demagnetization due to reverse armature field as well as the PM temperature rise. The model is a function of physical geometry and material of the PMSM, physics of demagnetization, and the ambient temperature. The demagnetization assessment and control is verified on a V-type PMSM using the modified FE-based coupled thermal-field-circuit phase variable model and the time step FE analysis.

Multiobjective Design Optimization of Coupled PM Synchronous Motor-Drive Using Physics-Based Modeling Approach

This paper deals with an optimal design of surface-mounted permanent magnet motor geometry for achieving minimum torque ripple, minimum RMS value of phase current, and minimum total harmonic distortion of phase currents, simultaneously. A classic multiobjective function is formed as a combination of these single objectives. A dynamic physics-based phase variable modeling approach is used to indirectly couple the motor geometry in the finite element domain to the drive circuit in a simulink environment. The physical behavior of motor is calculated by nonlinear transient FE analysis with motion. A fast hybrid genetic-particle swarm optimization process is developed for shape optimization of the motor. The results before and after optimization show the expected performance improvements while reducing magnet material and copper size.

HIL-Based Finite-Element Design Optimization Process for the Computational Prototyping of Electric Motor Drives

An online hardware-in-the-loop finite-element (FE)-based design optimization procedure is developed for the computational prototyping of coupled electric motor-drive system. A design optimization case for development of permanent magnet (PM) machine drive is presented. The physical representation of the machine is achieved by modeling the machine as a current adjustable load. The mutual interaction of the machine and the existing drive is taken into account by physical connection of the drive to a current adjustable load. The current adjustable load can be automatically renewed due to the design parameter changes of the machine being designed in an optimization process. The optimal design of the PM machine example is realized using the proposed technique and both numerical and test results are discussed.

A multi-physics multi-objective optimal design approach of PM synchronous machines

The design procedure of a PMSM includes employing functional models of the machine which reflect the thermal, electrical and magnetic aspects of the machine. In this paper, the complete process for creation of a physics-based model is presented. The model is employed in the heart of the multi-physics design optimization of a PMSM. The design optimization is accomplished by using a genetic-particle swarm optimization process. The design optimization using the physics-based model is applied on a surface mount PMSM. The initial and optimized designs are compared.

Sensorless Control of PM Synchronous Machines by Physics-Based EMF Observer

A sensorless rotor position estimation and speed control of three-phase radial flux surface-mounted permanent magnet synchronous machine (SMPMSM) is presented. A novel thermoelectric physics-based modeling approach was developed to evaluate more realistic information about the instantaneous behavior of the machine during operation. The extracted information from the physics-based models is employed in the back electromotive force observer. The mathematical modeling, stability, and transient analysis of the observer are developed and described in detail. The sensorless operation of a 0.2-kW SMPMSM was verified numerically and experimentally for medium low, low, and very low speeds at different operational contingencies. The results show that, in spite of significant machine model variations and increased noise level especially at very low speeds, the accuracy of estimated speed and rotor position using the developed observer is acceptable.

Inter-turn fault modeling of a variable speed pm wind generator using physics-based approach

Model-based approaches to the inter-turn fault diagnosis of electrical machinery cover three main categories: fault modeling, feature extraction, and classification. In this paper, the modeling of a PM generator with the internal permanent short circuit fault under speed variation is presented. For this purpose, the geometrical dimensions, winding arrangement, material, and phase resistance of a typical PM machine are designed. The designed values are used to create a physics-based phase variable model of the PM generator. The Physics-based phase variable model of the machine is created using the back emfs and inductances obtained from a nonlinear transient FE analysis of the machine. The permanent fault is modeled as a parallel resistance with some turns in one of the phases. The physics-based model of the machine includes information about the fault location and the number of turns which are shorted. The Physics- based phase variable generator model is then placed in a network consisting of a rectifier, dc bus, DC/AC converter, and a balanced AC load. The effects of variation in the number of shorted-turns, fault resistance, and speed on the voltages terminals of generator were studied. The simulated results show promising information for the identification of inter-turn faults and their classification for the diagnostic studies of a variable speed wind PM machine.

Analysis of Radiated EMI and Noise Propagation in Three-Phase Inverter System Operating Under Different Switching Patterns

In this paper, a numerical model using the finite-element (FE) method was used to predict the electromagnetic interference (EMI) generated by 325-V, 5-kW power inverter, supplying a variable three-phase load. A comparative analysis was performed to evaluate the effects of different switching patterns on the radiated and conducted EMI levels. An experimental setup was arranged to validate the simulation results. The proposed approach is suitable for prediction of radiated and conducted EMI generated by power converters. This helps reduce the post prototype EMC testing cost by minimizing redesign and modifications of final converter product.

Optimum Equivalent Models of Multi-Source Systems for the Study of Electromagnetic Signatures and Radiated Emissions From Electric Drives

An optimum equivalent electric machine model for 3-D finite element (3DFE) simulation and evaluation of radiated electromagnetic field emissions in a multi-machine environment is presented. A typical example of such systems includes electric motors and cable runs electric drives. Initially, the detailed geometrical model of the machine was simulated in a 3DFE quasi-static electromagnetic domain. An optimum equivalent model was created using an optimization process based upon the difference between the observed electric and magnetic far fields from both the detailed geometrical and the equivalent models. The equivalent model was validated in several examples. The computed electromagnetic signature results from the equivalent model show acceptable accuracy as compared with the detailed geometrical model of the machine. The equivalent machine model was obtained with significant reduction in computation time needed for the evaluation of the radiated fields. The proposed model can be used as an effective method for the simulation of signatures and radiated electromagnetic field emissions from electric drives in computationally intensive environments.