## 2 Materials and Methods
### Numerical Method  
To solve the composite electromagnetic problem, the electromagnetic field of the PEV inverter was calculated in Comsol Multiphysics 6.0 with the coaction of the DC input, high-frequency inverter, and AC output current, meeting the following equations:  
\[\
abla\times H=J \tag{2}\]  
\[B=\
abla\times A \tag{3}\]  
\[J=\sigma E+j\omega D \tag{4}\]  
\[E=-j\omega A \tag{5}\]  
where \(H\) is the magnetic field strength (A m\({}^{-1}\)); \(J\) is the induced current density (A m\({}^{-2}\)); \(E\) is the electric field strength (V m\({}^{-1}\)); \(B\) is the magnetic flux density (T); \(D\) is the electric flux density (C m\({}^{-2}\)); \(A\) is the vector magnetic potential (Wb m\({}^{-1}\)); \(\omega\) is the angular frequency; \(\mu\) is the relative permeability (H m\({}^{-1}\)); and \(\sigma\) is the electrical conductivity (S m\({}^{-1}\)). To achieve the best compromise between accuracy and computational efficiency, the inverter model was simplified, and only the most relevant parts were retained. The current was the only source of the magnetic field in the inverter. The simplified inverter was composed of two input DC wires, three inversion wires (simplified semiconductor model responsible for the inversion of the DC), and three output AC wires and encased in an aluminum alloy shell, as shown in Figure 4. In this study, the rated operating state of the inverter was used for numerical calculation, and the load was the 15 kW AC motor. So, the DC current in the DC wires was 34 A with a 350 V battery pack voltage, the AC current in the AC wires was 30 A\({}_{\rm rms}\) with a frequency of 100 Hz, and the high-frequency pulse current in the inversion wires was 45 A\({}_{\rm rms}\) with a frequency of 5.4 kHz. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Tissues of** & **Relative** & **Relative** & **Electrical** & **Relative** & **Electrical** \\
**Human Model** & **Permeability** & **Permitivity** & **Conductivity** & **Permitivity** & **Conductivity** \\  & & **(100 Hz)** & **(S/m) (100 Hz)** & **(5400 HZ)** & **(S/M) (5400 HZ)** \\ \hline Bladder & 1 & 192,840 & 0.21 & 12,467 & 0.21 \\ Bone & 1 & 217,030 & 0.08 & 2791 & 0.08 \\ White Matter & 1 & 1,667,700 & 0.06 & 19,793 & 0.07 \\ Cerebellum & 1 & 3,906,400 & 0.11 & 39,720 & 0.13 \\ Scalp & 1 & 45,298 & 0.0005 & 29,919 & 0.0015 \\ Heart & 1 & 3,163,700 & 0.09 & 120,170 & 0.14 \\ Kidney & 1 & 3,518,100 & 0.10 & 65,207 & 0.13 \\ Liver & 1 & 678,470 & 0.04 & 41,051 & 0.05 \\ Lung & 1 & 567,080 & 0.21 & 61,156 & 0.24 \\ Muscle & 1 & 9,329,000 & 0.27 & 47,982 & 0.34 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Dielectric parameters of the different tissues and organs of the human body. Then, the three-dimensional geometric models (the human body, vehicle, and inverter models) were divided into tetrahedral meshes [45; 46] in Comsol Multiphysics 6.0, which is a general numerical calculation tool for solving electromagnetic field problems. Based on Equations (2)-(5), the magnetic field interface under the AC/DC module of the Comsol Multiphysics 6.0 was adopted. The meshes of the human tissues and organs were divided more finely to improve the computing accuracy of the field distribution in different human tissues. In Comsol Multiphysics 6.0, the vehicle body model was divided into approximately 440,000 elements, and the human body model was divided into approximately 180,000 elements.