## 5 Experimental Verification
### Prototype Design and Testing Platform  
The experimental validation of the analytical model and finite element results was conducted using a purpose-built prototype and comprehensive testing apparatus at the High-Speed Electrical Machines Laboratory. The prototype motor was manufactured according to the optimized design specifications with key parameters: four pole pairs, 12 stator slots, five modulator segments, 30,000 rpm rated speed, 5 kW rated power, and a 0.8 mm air gap length. Figure 1 displays the key sub-assemblies of the high-speed magnetic field-modulated motor together with the integrated test bench that was built for model verification. The modulator ring in Figure 13a is a high-strength alloy sleeve in which several equally spaced ferromagnetic segments are press-fitted; this segmented construction provides the required spatial harmonics while withstanding the mechanical stress at the rated 30 krpm. Figure 13b shows the laminated silicon-steel stator core (M250-35A, 0.35 mm) whose slot openings and tooth-tip fillets were refined through finite element optimization to mitigate flux leakage and iron loss. The permanent magnet rotor, illustrated in Figure 13c, adopts surface-mounted NdFeB (N40 UH) magnets that are circumferentially constrained by a pre-stressed T700 carbon fiber sleeve, guaranteeing mechanical integrity under the high peripheral speed. A flywheel hub with dual inertia discs is presented in Figure 13d; the discs are shrink-fitted to a Ti-6 Al-4V shaft, supplying a 0.05 kg\(\cdot\)m\({}^{2}\) moment of inertia that emulates the storage rotor required by the flywheel energy system. The complete experimental rig is shown in Figure 13e: the prototype is connected to a 22 kW prime mover through zero-backlash diaphragm coupling, while a Magtrol HD-815 torque-speed transducer (\(\pm\)0.1% PS, \(\pm\)1 r min\({}^{-1}\)) and a Yokogawa WT5000 power analyser (0.01% reading) record mechanical and electrical outputs, respectively.  
Figure 13: The prototype high-speed magnetic field-modulated motor (HFMM) and the associated test bench: (**a**) the modulator ring with five equally spaced ferromagnetic segments press-fitted into a high-strength alloy sleeve; (**b**) the silicon–steel stator core (M250-35A, 0.35 mm) whose semi-closed slots were refined to suppress flux leakage; (**c**) the surface-mounted NdFeB rotor constrained by a pre-stressed carbon fiber sleeve; (**d**) the flywheel hub and Ti-6 Al-4V shaft assembly providing the required rotational inertia; (**e**) the complete experimental rig consisting of the prototype, a 22 kW primemotor, a Magtrol HD-815 torque–speed transducer, and ancillary instrumentation.  
All tests were conducted inside a 10\({}^{-2}\) Pa vacuum chamber at an ambient temperature of 22 \(\pm\) 1 \({}^{\circ}\)C. Sixteen Neoptix T1 fibre-optic probes (\(\pm\)0.2 \({}^{\circ}\)C) were embedded in the stator windings, stator core, permanent magnets, and modulator, and surface temperatures were tracked with a FLIR A655 sc infrared camera (FLIR Systems, Wilsonville, OR, USA, \(\pm\)2 \({}^{\circ}\)C). A National Instruments PXIe-1075 system sampled all electrical, mechanical, and thermal channels synchronously at 20 kHz.  
The fabricated prototype retains the electromagnetic specifications adopted in the analytical study--four pole pairs, twelve stator slots, five modulator segments, and a 0.8 mm air gap--and is capable of delivering 5 kW at the rated speed of 30,000 r min\({}^{-1}\), thereby providing a faithful platform for validating the coupled electromagnetic-mechanical-thermal models developed in this work.