TE - White Papers

TE Connectivity White Paper /// Thermal Modeling for High Power Charging (HPC) of Electric Vehicles Page 5 Thermal Modeling for High Power Charging (HPC) of Electric Vehicles with this type of load profile – which does not reflect reality – and a safety margin, for instance, of 20 per cent is added. The actual load profile in an EV, however, differs dramatically from previous vehicle applications and their RMS values (Fig. 2). Fig. 2 explains why thermal design is so essential for charging. While driv- ing results in a very dynamic current profile, consisting of load changes between high peaks and lows, the constant high load during HPC DC is not reflected at all in the load profile derived from driving. To facilitate a peak load of 350 kW charging pow- er, requires a different approach to designing the electrical components. While the electric energy stored in a battery is typically retrieved over a time span of several hours during driving, three to four times this amount of energy flows into the battery during HPC DC within min- utes. Accordingly, the complete high voltage / high current path has to be analyzed at a system level to under- stand its behavior during charging (Fig. 3). Root mean squares are not very helpful for this as is detailed above. It is essential to know where a con- stant load can cause over-heating that might lead to a critical system state. This thermal angle needs to be analyzed more closely. The methods currently employed do not deliver the answers. As a result, current systems are stat- ically over-dimensioned due to safe- ty considerations. With 350 kW of charging power, this approach is not sustainable due to the implications on weight, installation space, and usability. TE Connectivity is actively driving the development of a new design approach within its ZVEI activities (German Electrical and Electronic Manufacturers' Association). The tar- get is a methodology which dynami- cally determines the temperature in- crease caused by components and the heat dissipation in the system at all times via established principles of simulation (as used for electrical systems). This methodology makes it possible to examine the component design earlier in order to predict the component's performance during operation. It should be noted that the target is not to reduce safety margin. This new approach to design, based on systemic and near real-world ther- mal simulation, will facilitate a safe long-term operation as well as a design which enables improved us- ability. Model-based thermal simu- lation provides a verifiable basis for future load profiles which facilitate a proof of safety, reliability and Fig. 1: Quantification method behind the current profile in Fig. 2. Fig. 2: Driving profile compared to an HPC load profile. The aim of HPC is to compress a 300 km range into 10 min charging time, but the accel- eration factor 16x in time is equivalent to a multiplication of the heat dissipation by 256x Typical EV Drive Cycle Typical Battery Charging Profile

• Cover