The latest idea for reducing vehicle weight comes from the German engineering colossus Siemens, which has developed a way to integrate an EV’s motor and inverter in a single housing. An inverter, which converts the battery’s direct current into alternating current for the motor, is a key component of any EV.
Siemens’ Sivetec MSA 3300 integrated drive unit reduces weight, because only a single housing is needed, and it frees up six to seven liters of additional space. Integrating the two components also eliminates the costs of wiring the motor to the inverter, and means fewer assembly steps are needed to produce the vehicle.
One problem that the Siemens engineers faced was the heat generated by the electric motor. At high temperatures, the output of the IGBT modules, which convert the battery’s current into AC, has to be limited. For this reason, inverters in electric cars have their own water cooling systems, according to Siemens.
A key feature of the integrated drive unit was therefore the creation of a special cooling system. The coolest water first flows around thermally sensitive components such as the IGBT modules and the intermediate circuit capacitor, after which it is led into the motor’s cooling jacket. The water flow system is designed so that a kind of water screen is created between the inverter electronics and the motor, thermally isolating the two units from one another.
Another component of the solution is SkiN, a bonding technology that connects the surface of the semiconductor chip without requiring wire. When the thermal load fluctuates, the electrical contact between the chip and the bonding wire is a weak point of semiconductor components.