چكيده لاتين
Synchronous reluctance machines are sort of AC machines that are simpler and cheaper than other types of AC motors. However, these motors inherently have a low power factor and lower power and torque density compared to permanent-magnet motors. To overcome these disadvantages, the use of a small amount of permanent-magnet material in such motors can be effective, and this addition of magnets led to the emergence of PM-assisted synchronous reluctance machines, which are used in many applications instead of the pure synchronous reluctance motors. On the other hand, fractional-slot concentrated-windings (FSCWs) due to their higher slot fill factor, shorter end-winding length, low copper losses, high efficiency, simplicity and low manufacturing cost, have always attracted the attention of researchers. Because of low rate of harvesting of reluctance torque, these windings have not often been successfully used in the construction of this type of motors.
In this thesis, in order to increase the rate of harvesting of reluctance torque in these machines- which are equipped with FSCWs- by the means of stator slot shifting concept, a new type of fractional-slot concentrated-windings is introduced that simultaneously provides the capabilities of general distributed- and fractional-slot concentrated-windings. As an example, a 36-slot/10-pole fractional slot winding with two slot shifts is obtained from a 12-slot/10-pole winding, which contains much fewer MMF harmonics, such that the THD percentage of the MMF harmonics produced by the stator decreased from 89% in the 12/10 to 19% in the 36/10 arrangement. These new windings, including 3-phase and 5-phase windings, are introduced for the first time in this thesis and their winding’s layouts are exhibited here. These new windings include various combinations of pole and slot numbers, and while the MMF waveform produced by the stator is modified and its harmonics are greatly reduced, they retain the major advantages of fractional slot windings, including short end-winding length and low copper losses.
Based on these proposed winding configurations, one of the new 3-phase windings is selected, and a 180W prototype machine is designed and built as a case study; and analytical results, the finite element analysis, and experimental tests are conducted to validate the machineʹs characteristics. At the end, in order to improve the performance of the primary pure reluctance machine, magnets are inserted in the rotor flux barriers, and the results of simulations and practical tests show that not only the use of magnets improve the machineʹs power factor from 0.48 to 0.83, but the average torque produced by the machine also increases from 2.23 to 2.89 Nm.
