Study on the Selection of the Number of Magnetic Poles and the Slot-Pole Combinations in Fractional Slot PMSM Motor with a High Power Density

Abstract

Fractional slot, PMSM motors with a properly designed electromagnetic circuit allow for obtaining high power density factors (more than 4 kW per 1 kg of total motor weight). The selection of the number of magnetic poles to the specific dimensions and operating conditions of the motor, as well as the number of slots for the selected number of magnetic poles is the subject of the analysis in this article. This issue is extremely important because it affects the mass of the motor, the value of shaft torque, shaft power and the value of rotor losses. The aim of the work is to select solutions with the highest values of power density factor and, at the same time, the lowest values of rotor losses. The object of the study is a fractional slot PMSM motor with an external solid rotor core with surface permanent magnets (SPM). Motor weight is approximately 10 kg, outer diameter is 200 mm and a maximum power is 50 kW at 4800 r/min. The article analyzes the selection of magnetic poles in the range from 2p = 12 to 2p = 24 and various slot-pole combinations for individual magnetic poles. The target function of the objective was achieved and the calculations results were verified on the physical model. The best solutions were 20-pole, 30-slots (highest efficiency and lowest rotor loss) and 24-pole, 27 slots (highest power density).

Archives of Electrical Engineering

“…Their content can be limited by the appropriate selection of slot/pole combinations. This issue was presented in detail, in the work [21].…”

“…( 6)- (8). Therefore, when comparing solutions based on electromagnetic torque/power, erroneous conclusions can be drawn when the share of losses in the rotor and stator core in relation to the total losses is large [21].…”

“…Therefore, when comparing the presented solutions, it should be stated that the solution 𝑝 = 20, 𝑄 s = 30 with the coefficient 𝑞 = 0.5 is characterized by both high operating parameters of the motor and the lowest value of losses in the rotor despite the lowest value of the winding factor 𝑘 𝑤 . Moreover, according to [21], solutions with the number of slots 𝑄 s lower than the number of magnetic poles 2𝑝are characterized by the highest values of losses in the rotor and should be avoided, especially when operating with high values of supply frequency and high values of current loads. The above analysis shows the legitimacy of using two of the analyzed solutions, the variant 2𝑝 = 20, 𝑄 s = 24 and the variant 𝑝 = 20, 𝑄 s = 30.…”

Analysis of Impact of Design Solutions of an Electric Machine with Permanent Magnets for Bearing Voltages with Inverter Power Supply

“…The development of power electronic converters supplying electric motors contributed to the overall development of drive systems, enabling their operation at high supply frequencies, up to 1000 Hz [10]. One of the main sources of disturbances in drive systems is circuits with IGBT and MOSFET transistors.…”

Design and FEM Analysis of High-Torque Power Density Permanent Magnet Synchronous Motor (PMSM) for Two-Wheeler E-Vehicle Applications

“…On freezing the application of the PMSM as hub-motor, and the required power, voltage, and speed ratings, the design starts with freezing the selection of number of stator slots and rotor poles for the PMSM to yield the rated torque under the specified rated speed conditions. e appropriate selection of the slots and pole combination freezes the optimal electromagnetic circuit model of the PMSM [21]. e number of poles and slots can be selected from the chart, which is a part of the literature review of the well-defined principles [16].…”