Experimental Validation of Analytical Dynamic Characteristics of a Slotless Permanent Magnet Synchronous Motor Using a Dedicated Laboratory Test Bench

Abstract

Slotless permanent magnet synchronous motors are attractive for precision electric-drive applications because eliminating stator slots can suppress slotting-related torque disturbances; however, their analytical performance relationships require experimental verification under realistic drive conditions. This study experimentally validates the dynamic characteristics of a 1.7 kW, 10-pole slotless permanent magnet synchronous motor (PMSM) and evaluates its measured performance against a theoretical conventional PMSM benchmark. A dedicated laboratory test bench was used for multi-step, no-load speed tests and rated-speed load tests with synchronized acquisition of rotational speed, stator current, torque, drive-reported voltage, and mechanical power. At approximately 2000 rpm, the current-torque data were well described by I_s = 0.668T + 0.208 A (R2 = 0.9975); the coefficient of determination is used only as a statistical goodness-of-fit measure. Mechanical power reconstructed from P_m = Tω agreed with the torque-sensor power channel within approximately 0.04% mean absolute relative difference, confirming internal consistency of the mechanical data. At four matched torque points, the slotless prototype required 7.87% less current on average than the linear reference and exhibited an 8.70% higher effective torque-to-current ratio. Under an equal-resistance sensitivity assumption, the corresponding normalized current-squared indicator was 14.99% lower, on average. The results validate the proposed analytical-to-experimental method within the investigated operating range while explicitly identifying the benchmark and measurement limitations.