## 3 Results and Discussion  
As is known from analytical sizing, optimization, and numeric analysis studies, the BLDC motor that was designed and considered in this paper to evaluate performance is a 2.5 kW 32-pole in-wheel motor, which is used in small-size electric vehicles. The prototype  
Figure 11: Proposed multiphysics analysis scheme.  
Figure 10: Multiphysics analysis flowchart.  
motor and test bed are given in Figure 12. Experimental studies have been conducted to verify the motor performance obtained by design and simulation studies.  
Figures 13 and 14 present the comparative performance evaluation of the optimal motor with simulation results and experimental results. As a result of experimental studies, the targeted performance values were obtained when the values presented in Table 4 were examined. The motor performance has been analyzed according to the rated operation. At a 96 V operating voltage, the motor yields a nominal 26.61 Nm torque, nominal 2.5 kW power, and nominal 91.37%, efficiency. The deviation rate is quite small, and this indicates that the experimental results agree with the simulation results. The differences that occur may be due to several reasons. These are as follows: simulation may not fully include driver losses in the model; in experimental work, switching losses of MOSFETs or IGBTs, voltage drops, conduction losses, and heating effects may reduce efficiency; friction in bearings in experimental tests may significantly reduce efficiency at low speeds; and torque, current, and voltage sensors have a certain margin of error in actual experiments.  
Figure 14: Comparison at each output power: (**a**) rated torque; (**b**) efficiency.  
Figure 13: Comparative performance evaluation; (**a**) simulation results; (**b**) experimental results.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & \multicolumn{2}{c}{**Optimum Design**} & \multirow{2}{*}{**Experimental**} & \multirow{2}{*}{**Deviation Rate**} \\  & **Simulation** & & \\ \hline V [V] & 96 & 96 & 0 \\ \hline I [A] & 28.458 & 30.05 & 0.05 \\ \hline T [Nm] & 27.36 & 26.61 & 0.028 \\ \hline n [rpm] & 873 & 897 & 0.026 \\ \hline Pin [W] & 2725 & 2737.372 & 0.004 \\ \hline Pout [W] & 2500 & 2500.91 & 0 \\ \hline Efficiency & 91.74\% & 91.36\% & 0.004 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Performance data at rated operating condition.  
In Figure 15, the thermal analysis results of the motor and the experimental results are given comparatively. The temperature values of motor parts are given in Table 5. In the experimental study, the temperature distribution and values of the motor were obtained by thermal imaging after the motor was operated at full load for 5 min. Considering both simulation and experimental results, the winding temperature was approximately 72 \({}^{\circ}\)C, and the average temperature was 50 \({}^{\circ}\)C. As expected, the core's temperature is in direct contact with the windings, which is higher than the yoke's. There is a difference of approximately 1 \({}^{\circ}\)C between the temperature value obtained after the experimental measurement and the steady-state simulation estimate. There are some limitations in directly comparing the results of the short-term steady-state simulations with the experimental study. These limitations include transient thermal effects and potential sources of inconsistency (e.g., convection effects, material thermal properties, and environmental factors). In addition, although the simulations were performed based on steady-state conditions, the iteration value was kept small due to the long calculation times in 2D and 3D integrated electromagnetic-thermal analyses, and the analysis was performed in a relatively short run time. This situation caused a difference between the results obtained before the model reached full thermal equilibrium and the experimental measurements.  
Figure 15: Comparative thermal evaluation; (**a**) simulation results; (**b**) experimental results.