Papers by Essam Eddin M . Rashad
Nowadays, a growing interest in the efficiency and the cost of electrical machines has been notic... more Nowadays, a growing interest in the efficiency and the cost of electrical machines has been noticed. Therefore, Synchronous Reluctance Motors (SynRMs) have become more attractive, thanks to their higher efficiency and nevertheless acceptable cost compared to induction machines. The rotor design of SynRMs with or without permanent magnets (PMs) has a huge effect on the motor efficiency, torque density and power factor. This paper introduces an evaluation for the performance of SynRMs with and without PMs in terms of efficiency, torque and power factor maps. Three different rotor designs for the same machine have been compared. For one machine, the experimental measurements have been obtained and the validation of the simulation results have been confirmed.
2015 IEEE Magnetics Conference (INTERMAG), May 1, 2015
This paper investigates the influence of various electrical steel grades on the torque and effici... more This paper investigates the influence of various electrical steel grades on the torque and efficiency of synchronous reluctance motors (SynRMs). Four different steel grades are studied for the same motor geometry. A finite-element method is combined with an experiment-based magnetic material model to study the effect of the four steel grades on the performance of the SynRM. On the one hand, there is a negligible effect on the torque ripple because this ripple depends mainly on the motor geometry. On the other hand, it was found that the material properties have an obvious effect on the SynRM efficiency and output power. Evidently, the low loss grades result in higher efficiency: 9% point higher for NO20 compared with M600-100A. One of the four considered grades is designed to have a higher flux density in the useful magnetic field range (a few hundreds to a few thousand amperes per meter). This grade has somewhat lower efficiency, but results in a higher saliency ratio and an 8% higher torque output compared with the worst grade. Some experimental validation results are shown.
This paper investigates the influence of the magnetic saturation on the transient performance of ... more This paper investigates the influence of the magnetic saturation on the transient performance of Synchronous Reluctance Motors (SynRMs). In addition, the stability limits for the SynRM are studied using a more accurate model. The saturation, cross-saturation and position effects on both direct (d) and quadrature (q) axis flux linkages are considered. A Finite Element Method (FEM) is used to obtain an accurate representation for the dq-axis flux linkages relations. In order to reduce the calculation time of the finite element analysis, a look-up table (LUT) for the dq-axis flux linkages is generated based on the FEM to be used for simulating the SynRM characteristics. It is found that the magnetic saturation in the adopted motor results in an enlarged region of stable operation of the SynRM. The torque increases by about 200 % compared with the unsaturated case, which proves that it makes no sense to model this type of motor without saturation. The results show the importance of including the saturation factors on the performance of the SynRM and its stability limits. Hence, the magnetic saturation effect will not only affect the stability of the motor but also on the whole drive system.
IOP Conference Series: Materials Science and Engineering, 2020
Nowadays, a great interest in the efficiency and the cost of electrical machines has been noticed... more Nowadays, a great interest in the efficiency and the cost of electrical machines has been noticed. Therefore, Synchronous Reluctance Motors (SynRMs) have become more attractive alternative for induction and permanent magnet (PM) synchronous machines in several industrial applications. This is because they do not use rare-earth magnets, windings and cages in their rotor. Consequently, the cost and efficiency are improved. Nevertheless, a major problem of the SynRMs is the low power factor. To improve the power factor as well as the torque density and efficiency, the cheap ferrite PM can be inserted in the rotor, resulting in the so called ‘PM assisted SynRM’. The rotor design of SynRMs with and without permanent magnets (PMs) has a huge effect on the motor efficiency, torque density and power factor. This paper introduces an evaluation for the performance of SynRMs with and without PMs in terms of efficiency, torque and power factor maps as a consequence of different rotor designs. T...
IEEE Transactions on Industry Applications, 2023
alexandria engineering journal, Sep 1, 2023
2023 IEEE Conference on Power Electronics and Renewable Energy (CPERE)
2022 25th International Conference on Electrical Machines and Systems (ICEMS)
Energies
Inverters with Quasi-Z-Source Networks (QZSN) provide DC-DC boosting and DC-AC conversion in a si... more Inverters with Quasi-Z-Source Networks (QZSN) provide DC-DC boosting and DC-AC conversion in a single stage. It offers reduced cost, complexity, and volume compared with the classical two-stage conversion system, which is composed of a boost converter followed by a Voltage-Source-Inverter (VSI). Further, QZSI provides superior conversion characteristics for single-stage grid-connected photovoltaic transformerless systems. However, the absence of galvanic isolation in these systems makes it possible to allow leakage current through these systems’ parasitic capacitances due to the high-frequency Common-Mode Voltage (CMV) generated by the Pulse Width Modulation (PWM) nature of the inverter output voltages. As a result of this current, critical safety issues may arise with PV systems. Many PWM techniques have been presented in recent years for QZSIs. This paper is intended to provide a comprehensive analysis and review study of the characteristics of most of these PWM techniques in term...
IEEE Transactions on Industrial Electronics
IEEE Transactions on Industry Applications
IEEE Transactions on Industry Applications
IEEE Transactions on Power Electronics
2021 22nd International Middle East Power Systems Conference (MEPCON), 2021
This paper presents an impartial comparison of the dynamic behavior of permanent magnet synchrono... more This paper presents an impartial comparison of the dynamic behavior of permanent magnet synchronous motors (PMSM) under three control techniques i.e., model predictive current control (MPCC), model predictive direct speed control (MPDSC) and field-oriented control (FOC). In MPCC, the voltage vectors applied to the inverter are determined by minimizing a cost function comprising the error in currents; whereas, in MPDSC, the voltage vectors applied to the inverter are determined according to minimization of cost function which includes speed and current errors. In MPCC, PI controller is used to regulate the speed, whereas in the MPDSC, there are no PI controllers. When the FOC is applied, modulated voltage vectors are determined according to three PI controllers for speed and current control. Most crucial implementation issues, which affects the dynamic performance of PMSMs, are addressed during the comparison between three control techniques. These issues include delay time, switching frequency and parameters mismatch. The delay time, due to the large number of calculations, is compensated by predicting the state variables two sampling intervals ahead. Switching frequency is included in the objective function to reduce switching losses. The effect of delay time and switching frequency is related to MPCC and MPDSC; meanwhile parameters mismatch is associated with all control methods. The dynamic behaviors are assessed via simulation results at different load conditions. The final evaluation was performed in terms of rising time, settling time, total harmonic distortion and average switching frequency.
Computers & Electrical Engineering, 2021
2016 IEEE International Conference on Power and Energy (PECon), 2016
In the sub-synchronous mode, series-connected wound-rotor induction motor can run at a speed belo... more In the sub-synchronous mode, series-connected wound-rotor induction motor can run at a speed below the synchronous speed with self-starting capability in a manner similar to that of the normal mode of operation of an induction motor. Under proper conditions, operation in the series-connected mode can achieve better characteristics compared with normal induction motor by short-circuiting rotor circuit. Based on a developed mathematical, this paper investigates the effect of machine parameters on steady-state characteristics of series-connected wound-rotor induction motor sub-synchronous mode. A special attention is given to stator and rotor winding resistances along with stator-to-rotor effective turns ratio. The obtained results represent a helpful guide for designing wound rotor induction motor for operation in series-connected sub-synchronous mode.
2016 IEEE International Conference on Power and Energy (PECon)
The wound-rotor induction machine is capable of electromechanical energy conversion, if the stato... more The wound-rotor induction machine is capable of electromechanical energy conversion, if the stator and rotor windings are connected in series with a proper phase sequence. As a motor, the operation can be in one of two modes. In the first mode, the motor runs at exactly twice the synchronous speed for stable loading conditions. In the second mode, the motor runs at a speed below the synchronous speed (sub-synchronous) with self-starting capability in a manner similar to that of the normal operation mode as an induction motor. In this paper, the operation of the motor in the sub-synchronous mode is analyzed using the physical relationships between the stator and rotor mmfs. The analysis includes the calculation of losses and efficiency. The obtained laboratory experimental results proved the validity of the proposed analysis.
IEEE Transactions on Energy Conversion
2019 IEEE Conference on Power Electronics and Renewable Energy (CPERE)
Recently, multiphase drive systems have been proposed for special applications where high reliabi... more Recently, multiphase drive systems have been proposed for special applications where high reliability is required. Asymmetrical Six-Phase Induction Machine (ASPIM) is one of the most important particular multiphase machines due to many distinctive features. The two-level six-phase Voltage Source Inverter (VSI) is commonly used to supply the ASPIM. However, it has the main conceptual shortcoming of voltage gain limitations. Z-Source Inverter (ZSI) is developed in this paper to overcome the voltage gains shortcomings of standard VSIs. Carrier-based PWM schemes with simple and maximum boost control methods are utilized here to control the shoot-through duration of the ZSI, which is used to supply ASPIM. In addition, new carrier-based modulator to reduce the inverter switching losses is proposed in this paper. This strategy can be extended to other types of impedance network-based six-phase VSI. The operating principles, theoretical analysis and comparative study of the presented PWM schemes are introduced. The feasibility of the proposed PWM schemes and the performance of the drive system are confirmed by the simulation results which show good agreement with the analysis.
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Papers by Essam Eddin M . Rashad