Mohamed Nabil Fathy Ibrahim

Synchronous reluctance motors performance based on different electrical steel grades

Recently, the Synchronous Reluctance Motor (SynRM) has received more attention for many applications, thanks to its rugged construction and low cost [1]. Over the past decades, developments in machine design methodology, high quality magnetic materials, and advanced power electronics allow the machine designers to enhance the performance of the SynRM which depends mainly on the direct and quadrature axis inductances (Ld, Lq). Therefore, considerable attention has been given to improve the saliency ratio of the SynRM, taking into account the core material and its saturation behaviour. Several papers have focused on the rotor geometry design and the saturation effect on the performance of the SynRM [2, 3]. However, the effect of the electrical steel grades on the performance of the SynRM has not been deeply studied.

Combined Star-Delta Windings to Improve Synchronous Reluctance Motor Performance

This paper analyzes and compares the synchronous reluctance motor (SynRM) performance for a conventional star winding and for a combined star-delta connected winding under healthy and faulty conditions. The finite element method is used to simulate the SynRM characteristics in case of normal star and in case of combined star-delta connected windings. For the healthy case, it was found that for the same current, the SynRM output power increased by about 5% for the star-delta connected windings compared with the conventional star connection. Moreover, the efficiency increased slightly by 0.20%. Probably the strongest advantage of the combined star-delta winding is observed when a phase fault occurs. When one phase is missing, for the same current, the star-delta connected motor keeps 80% of the rated torque in the healthy case, while the star connected motor only keeps 40%. Furthermore, the torque ripple of the star wound machine is extremely high in case of a missing phase, compared to the star-delta wound machine. Simulation results were validated by experimental results to show the effectiveness of the star-delta connected windings on the SynRM.

Influence of rotor flux-barrier geometry on torque and torque ripple of permanent-magnet-assisted synchronous reluctance motors

The rotor design has a large effect on the performance of Permanent-Magnet-Assisted Synchronous Reluctance Motors (PMaSynRMs). An optimized rotor geometry is necessary in order to obtain higher motor torque with minimum torque ripple. This paper investigates the influence of the flux-barrier design which is the most important rotor geometry parameter regarding the torque and torque ripple of PMaSynRMs. The flux-barrier parameters are angle, width, and position, as well as the length. Starting from the optimized rotor of a SynRM without magnets, a PMaSynRM is created by inserting permanent-magnets inside the center of the flux-barriers. For a prototype SynRM, experimental results have been obtained to validate the FEM results and to validate the strategy for choosing the rotor parameters.

Transient analysis and stability limits for synchronous reluctance motors considering saturation effects

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.

Steady-state analysis and stability of synchronous reluctance motors considering saturation effects

This paper investigates the influence of the magnetic saturation on the performance of a Synchronous Reluctance Motor (SynRM) at steady-state. In addition, the stability limits for the SynRM are studied using a suggested more accurate method. The saturation and cross-saturation 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 by about 200 % compared with the unsaturated case. 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 reflect on the stability of the motor but also on the whole drive system.

An Improved Torque Density Synchronous Reluctance Machine With a Combined Star–Delta Winding Layout

This paper investigates the performance of synchronous reluctance motors when the stator is equipped with a combined star–delta winding layout. The conventional star winding is used as a benchmark in this study to compare different possible single-layer winding layouts. Among these different winding layouts, those which maximize the fundamental magneto-motive force component are selected. A simple mathematical formula is then derived to calculate the equivalent winding factor for different shares between star and delta subwindings. It has been proved that for the same copper volume and line current magnitude, the star–delta connection can offer an enhancement in the torque density of approximately 5.2% over the conventional star case under rated conditions. However, this gain is affected by the employed number of poles and stator slots. On the other hand, the effect of the winding layout on either power factor or core loss can be merely neglected over a wide range of speeds and currents. Nevertheless, the machine efficiency under a combined star–delta connection is relatively improved under light loading as a result to the machine torque/current ratio enhancement. The theoretical findings are experimentally validated using two identical 5.5 kW prototype machines, having star and combined star–delta winding connections.

Comparison between two combined star-delta configurations on synchronous reluctance motors performance

This paper compares the performance of Synchronous Reluctance Motors (SynRMs) using two different star-delta winding connections under normal operation. All the machine parameters are kept the same while the winding layout is only modified. The compared winding layouts differ in the combination between the number of coils of the star and delta winding sections. The two adopted windings are the only possible configurations that can give a high quality mangetomotive force (MMF) distribution. Experimental validation on a prototype SynRM with one winding is given, showing a good agreement with the theoretical findings.