## 3 Results and Discussion
### Effect of Inlet Velocity
traction inverter in the case of without backflow and with backflow are shown in Figure 7. The backflow affects the cooling of the traction inverter such that the inverter maximum temperature is high in the case of backflow compared to without backflow. In ferrofluids, natural convection can be influenced by the magnetic field, causing the ferrofluid to flow differently than it would in the absence of a magnetic field. However, in the present MHD pump-based cooling system, the ferrofluid experiences heat transfer through mixed convection phenomena because the MHD pump offers Lorentz force as a combination of magnetic and electric fields. In ferrofluids, when the magnetic and electric fields create a driving force for fluid motion, it augments the natural convective forces. Therefore, the heat transfer in ferrofluid is dominated significantly by mixed convection and superior compared to natural convection, due to presence of both magnetic and electric fields through the MHD pump. Furthermore, in cases when the conventional pump is enabled using constant velocity coolant path in addition to the MHD pump, the heat transfer in ferrofluid could even transit from mixed convection to forced convection. The comparison of the inverter maximum temperature for water and ferrofluid cooling considering various conditions of inlet velocity and voltage is shown in Figure 8. The MHD pump does not contribute to the circulation of water, therefore, with change in voltage, the inverter maximum temperature remains constant for each inlet velocity in the case of water cooling. The lack of self-circulation in the case of the water cooling results in higher inverter maximum temperature, however, the constant velocity coolant path  
Figure 7: (**a**) Flow streamlines in cooling channel with backflow, (**b**) Flow streamlines in cooling channel without backflow, (**c**) Inverter temperature with backflow and (**d**) Inverter temperature without backflow. contributes to circulating water, hence, the inverter maximum temperature decreases with an increase in inlet velocity because the heat transfer rate improves with a rise in velocity for water cooling. To ensure the efficient and safe operation of the inverter, the maximum temperatures of junction and casing should be maintained within the ranges of \(-20\)\({}^{\circ}\)C to \(150\)\({}^{\circ}\)C and \(-20\)\({}^{\circ}\)C to \(100\)\({}^{\circ}\)C, respectively. The inverter maximum temperatures of \(169.84\)\({}^{\circ}\)C, \(123.7\)\({}^{\circ}\)C, \(97.37\)\({}^{\circ}\)C, \(810.05\)\({}^{\circ}\)C, and \(49.65\)\({}^{\circ}\)C are evaluated for water cooling with inlet velocities of \(2\) mm/s, \(3\) mm/s, \(4\) mm/s, \(5\) mm/s, and \(10\) mm/s, respectively. The inverter maximum temperature for ferrofluid cooling is lower compared to water cooling for each inlet velocity because the contribution by the MHD pump's addition to the constant velocity coolant path for the circulation of ferrofluid results in lower inverter maximum temperature. Furthermore, the circulation of ferrofluid becomes significantly higher with a rise in voltage, which results in superior heat dissipation rate at a higher voltage. Therefore, with an increase in voltage, the inverter maximum temperature decreases.