{"id":25373,"date":"2021-03-22T08:59:20","date_gmt":"2021-03-22T12:59:20","guid":{"rendered":"https:\/\/blogs.sw.siemens.com\/simcenter\/?p=25373"},"modified":"2026-03-26T06:44:11","modified_gmt":"2026-03-26T10:44:11","slug":"ev-inverter-heart-analogy","status":"publish","type":"post","link":"https:\/\/blogs.sw.siemens.com\/simcenter\/ev-inverter-heart-analogy\/","title":{"rendered":"Inverters: the heart of electric vehicles"},"content":{"rendered":"\n

The electric vehicle inverter is an essential organ of the powertrain, yet it is often overlooked compared to batteries or electric machines. Looking at this study from NAS (2010), it is the most expensive component of a PHEV, second only to the battery.<\/p>\n\n\n

\n
\"\"\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Figure 1: Cost breakdown analysis of a Plug-in Hybrid Electric Vehicle – NAS (2010)<\/figcaption><\/figure><\/div>\n\n\n

Based on this, it must be carefully engineered. This is what is described in this post.<\/p>\n\n\n\n

Simcenter Amesim and the analogy with the human heart<\/h2>\n\n\n\n

Why the heart? Because it drives the blood (i.e. energy or electricity) across the different organs (i.e. electric motor, battery, on-board charger, etc.).<\/p>\n\n\n\n

And just like the heart chambers and ventricles pump blood throughout the body, the inverter\u2019s transistors and diodes pump electrons in and out of electrical circuits. The blood pressure is equivalent to the voltage level and you will need to have a high enough pressure for the blood to be able to properly irrigate your brain.<\/p>\n\n\n\n

Simcenter Amesim, leading system simulation solution for electrification, allows you to compare different voltage levels of an electric vehicle<\/strong> and see the impact on current levels, current quality and powertrain efficiency.<\/p>\n\n\n

\n
\"Simcenter\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Figure 2: Simcenter Amesim DC current comparison 400V vs 800V<\/figcaption><\/figure><\/div>\n\n\n

Once the voltage level is defined, we can select the transistors\u2019 technology, typically an IGBT or a MOSFET.<\/p>\n\n\n\n

This can be done in two ways in Simcenter Amesim: either import data coming from a datasheet or import conduction and switching waveforms coming from Xpedition AMS<\/a> or PartQuest Explore<\/a>.<\/p>\n\n\n

\n
\"Xpedition\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Figure 3: Xpedition AMS semiconductors characteristics import<\/figcaption><\/figure><\/div>\n\n\n

The comparison of different transistors and their impact on the electric vehicle range is deduced from the system simulations. Here for a midsize electric vehicle with a 68 kWh battery on SFTP-US06 driving cycle:<\/p>\n\n\n

\n
\"Simcenter
Figure 4: Simcenter Amesim vehicle range comparison IGBT vs SiC MOSFET <\/figcaption><\/figure><\/div>\n\n\n

Inverter switching frequency importance<\/h2>\n\n\n\n

The electric vehicle inverter switching frequency is like the BPM (beats per minute) and, like a doctor with a stethoscope, Simcenter Amesim can assess the noise vibration and harshness behavior of an inverter using a spectral map:<\/p>\n\n\n

\n
\"Simcenter
Figure 5: Simcenter Amesim e-motor torque ripple spectral map<\/figcaption><\/figure><\/div>\n\n\n

Here, the impact on the torque ripple of the electric machine is observed. The electric vehicle inverter switching frequency is 10 kHz and its first harmonic is observed at 20 kHz.<\/p>\n\n\n\n

On the electric side, high frequency current fluctuations are called current ripple. To avoid ripple propagating through the DC bus, a DC link capacitor is needed. It will become the preferable path for high frequency AC.<\/p>\n\n\n

\n
\"DC
Figure 6: DC link capacitor illustration<\/figcaption><\/figure><\/div>\n\n\n

The DC link capacitor is also used to stiffen the DC voltage i.e. reduce the ripple voltage.<\/p>\n\n\n\n

Increasing the switching frequencies require smaller DC link capacitors, leading to smaller components and to a higher power density for the inverter. Here is a comparison of voltage ripple for different switching frequencies<\/strong>, with a DC link capacitor of 0.005 F:<\/p>\n\n\n

\n
\"Simcenter
Figure 7: Simcenter Amesim voltage ripple analysis for different switching frequencies<\/figcaption><\/figure><\/div>\n\n
\n
\"Simcenter
Figure 8: Simcenter Amesim voltage ripple analysis zoomed<\/figcaption><\/figure><\/div>\n\n\n

Electric vehicle inverter thermal management<\/h2>\n\n\n\n

Increasing the switching frequency (the BPM), will lead to more heat released by the heart. Since the inverter is a complex piece of engineering, accurately capturing its transient thermal behavior requires either a 3D CFD or a testing approach<\/strong>. Indeed, some inverter locations like a transistor\u2019s junction temperature can face hot spots. Temperature can go beyond specified limits and the semiconductor can fail or accumulate thermal fatigue.<\/p>\n\n\n\n

To accurately identify these hot spots in Simcenter Amesim, two model reduction techniques are available: <\/p>\n\n\n\n