Does the 800V power module use IGBT or SiC devices?

I always thought that Taycan used Delphi's SiC devices, but according to what Hitachi AMS has disclosed, including what is described in the maintenance manual of Taycan, this is not the case.

Figure 1 Voltage and power system after 2020

01. IGBT module at 800V

The original text of this report is "High Voltage and High Power Density Technologies for Inverter in Vehicle". 

Figure 2 Information source 

The most surprising part here is that Taycan uses the original IGBT module, as shown below. The inverter developed by Hitachi AMS has improved the overall insulation design. The core is to improve and launch a power module suitable for 800V on the basis of the previous one. The new power module matches the 800V system and achieves a power density of 94kVA/L. To increase the system voltage from 400V to 800V, the main thing to do at the power module level is to improve the voltage resistance level. By optimizing the module packaging design and the insulation structure used, the size of the module is avoided. The power module is composed of two power elements in series and adopts a two-in-one package. Components such as IGBT and lead frame are sealed with transfer molds and further encapsulated in an aluminum module housing with double-sided cooling. 

Figure 3 Hitachi IGBT module
 

Figure 4 Hitachi's double-sided cooling technology entered its mature stage around 2015 

In terms of insulation treatment, in addition to completely covering the insulator on the electrode to which the high voltage is applied for insulation, insulation can also be achieved by setting the insulation distance, but it is necessary to ensure both the spatial distance and the creepage distance. In order to extend the creepage distance of the insulating resin part, ribs and grooves are added, and a chamfer shape is set at the end of the bus. The cross-sectional view of the resin insulation part in the figure below shows that the copper bus of the power module is separated by the insulating resin. In order to extend the creepage distance, in addition to increasing the height of the resin in the vertical direction, a gap is also made where the insulating resin contacts the bus to ensure the creepage distance. 

Figure 5 Insulation design of power module

The power module resin sheet insulates the lead frame and heat sink to which the power device is welded. The resin sheet is filled with a large amount of ceramic filler responsible for heat conduction to the heat sink, and has been made thinner to ensure high heat dissipation performance. However, since the small gaps generated when the insulating sheet is bonded to the lead frame and heat sink may cause a decrease in dielectric strength, the conductor foil is laminated inside the insulating sheet. The insulating sheet used in the power module is stacked with conductor foil inside to prevent partial discharge. When the voltage applied to the air layer in the gap is higher than the dielectric breakdown voltage of the air, partial discharge occurs. The electric field in the gap is reduced by dividing the voltage applied to the insulating sheet with the conductor foil. The potential difference between the conductor foil, the lead frame and the heat sink is divided to the upper and lower insulating sheets, and the potential of the conductor foil is fixed to the middle potential, improving the partial discharge characteristics of the insulating sheet. 

Figure 6 Design of insulation characteristics 

02. Use and path of SiC

In terms of organizing the 11kW AC charger, the H-bridge circuit part here should all be made of SiC devices, including the DC charging piles that Porsche itself subsequently adopted also used SiC modules. 

Figure 7 SiC usage in AC chargers

The article "4E Power Electronic Conversion Technology Annex" provides some usage paths for SiC, which may be useful for reference. 

Summary: I used to think that Taycan was the first car model to use a full set of SiC. From the beginning of Taycan's development to its mass production in 2019, we can see that Porsche engineers were hesitant about using the not-so-mature technology of the drive inverter. By 2022, the PPE platform will make extensive use of SiC technology.