# Design and Verification of Multiphase Multilevel Traction Inverter
## 4 Conclusions  
This paper presents the design process of a 6-phase TNPC multilevel inverter. The topology was selected based on the simulation results of the other papers and the research. Then, the design process is described in detail, describing the design of the power IMS board with all power semiconductors. The IMS board was selected due to its low thermal resistance and excellent heat transfer from the semiconductor to the heatsink. The measurement also proved this because the inverter was only passively cooled at the output power of 25 kVA. Other presented boards are driving and interconnection, which are driving the power MOSFETs based on the signals from the control board. The control board is designed as a 4-layer PCB consisting of all auxiliary power supplies and control DSP with signal conditioning. Additionally, the communication and resolver interfaces are present on this board. The BUS-BAR board was designed with thick copper layers to ensure low resistance and copper trace capacity to deliver the required power to the individual modules connected to the power supply. Other boards are current measurement and auxiliary boards.  
The measurement was done in the laboratory conditions with the passive R-L load simulating drive, with the \(\cos\varphi\) set to 0.82. The load was capable of dissipating 20 kW. The inverter was tested at seven input voltages ranging from 100 V to 500 V. The higher input voltage was impossible due to the absence of a high-voltage input power supply. As shown in Figure 13, the efficiency at the output power of 20 kW was from 99.18% to 99.37%, depending on the switching frequency. The final switching frequency for this prototype was selected to be 20 kHz because it offers good efficiency, and the inverter does not produce an audible noise during the operation. The efficiency maps shown in Figure 14 through Figure 16 show flat efficiency at high output power, indicating a perfect power module design. Additionally, the inverter was only passively cooled, and at maximum power output of 20 kW, the temperature of the module was around 53.5 \({}^{\circ}\)C.  
The following work will focus on additional testing. A more powerful load must be provided to fully test the converter-rated power output. Especially at this power output  
Figure 22: Load temperatures at 20 kW.  
level, the load should actively recuperate power from the grid. Additionally, a power supply with higher output voltage and power must also be provided for further testing. Implementation of the Field Oriented Control (FOC) is planned to this inverter, due to the advantages it offers compared to the SPWM. FOC offers decoupled control of torque and flux, which results in more accurate and dynamic response in motor control applications. Additionally, the FOC has reduced harmonic distortion compared to the SPWM method. For this control the on-board resolver/encoder interfaces will be used.  
Conceptualization, P.R. and S.K.; methodology, P.R. and M.P.; software, P.R.; validation, S.K. and P.R.; formal analysis, S.K.; investigation, P.R.; resources, P.R.; data curation, P.R. and S.K.; writing--original draft preparation, P.R. and S.K.; writing--review and editing, P.R., S.K. and M.P.; visualization, P.R.; supervision, M.P.; project administration, P.R. and S.K.; funding acquisition, M.P. All authors have read and agreed to the published version of the manuscript.  
This work was supported by projects APVV-22-0330, Research of a system for active and optimal management of electrical energy using battery storage system, and VEGA 1/0314/24, Research of a system for active management of electrical energy using the battery storage system. This research was also supported by the University of Zilina, UNIZA Grant Project: \"Research of methods for investigation of operating and fault conditions of drives with multiphase asynchronous motor\".  
Not applicable.  
The data are contained within the article.  
The authors declare no conflicts of interest.