Abstract
Mandatory regulations are published worldwide for the efficiency of line-operated electric motors. The small-sized single-phase induction motors (SPIMs) will not be off the hook in terms of efficiency, since new regulations are scheduled to be introduced regarding them no later than July 2023. By doing so, the efficiency of capacitor-run SPIMs will be forced to exceed the (currently) typical ratings and comply with the requirements of the IE3 (i.e., premium) efficiency class. Since this task is challenging, the already published research works investigated several design, control, and manufacturing aspects. Nevertheless, less attention has been devoted to the study of the rotor bar’s shape impact, both on the SPIMs’ efficiency and starting capability. This gap is filled in this work by examining rotor squirrel-cage configurations with eight different bar shapes for the case of a four-pole/1.0 HP capacitor-run SPIM. A sensitivity analysis, which involves the simultaneous variation of the bar’s cross-sectional area, run-capacitor value, and auxiliary to main winding turns ratio, is performed. The motor’s electromagnetic behavior is estimated through finite element analysis. Through the acquired results, useful directions toward the SPIMs’ efficiency enhancement are provided, while simultaneously conclusions—not found elsewhere—are drawn concerning performance quantities, such as the motor’s starting current, currents shift angle, particular losses, breakdown torque, etc.
Highlights
The single-phase induction motors (SPIMs) hold a considerable share of the global electrical machines market, as they are utilized in an impressive number of applications [1]
It has to be noted that the nominal rotational speed of the developed SPIMs remains almost constant for given k bar
It is reported that the efficiency of the SPIMs with the trapezoidal bars declines by up to 2.0% as the k bar varies from 0.2 to
Summary
The single-phase induction motors (SPIMs) hold a considerable share of the global electrical machines market, as they are utilized in an impressive number of applications (e.g., power tools, compressors, vacuum cleaners, conveyor belts, sewing and washing machines, grinders, refrigerators, food mixers, microwave ovens, air conditioners, hair and grain dryers, heating-circulating pumps, fans, centrifugal pumps, etc.) [1]. In order to improve the SPIMs’ efficiency, so far, research efforts have focused on (a) the introduction of more accurate magnetic and thermal models for the better estimation of the motor’s electromagnetic and thermal behavior [13,14], (b) the optimal rotor squirrelcage design [15,16,17], (c) the proper selection of the rotor bars/stator slots combination for a given number of poles [18], (d) the utilization of manufacturing techniques such as the skewing and inclination of rotor bars [19], (e) the appropriate choice of run-capacitor features (i.e., its optimal value and placement) [20,21], (f) the proposal of novel topologies [22], (g) the testing of advanced electrical steels and conductive alloys for the motor’s cores and squirrel-cage, respectively [23,24], and (h) the application of new casting methods [25]. It is to be noted that the new efficiency levels are achievable with the present technology and by taking into consideration the standardized frame sizes
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