The Power loss of the Wave-sculptor 22 motor controllers is given by the following equations where:
Ploss = Req*Io2 + (α*Io+β)*Vbus + Cfeq*V2bus
| Description | Value | |
|---|---|---|
| Vbus | Bus (Battery) Voltage of the controller | 129.6V Nominal (100V - 151.2V) |
| Io | Ouput current of the controller | Pmax/Vbus (Roughly, This will actually be off by ~1.2x) |
| Req | Equivalent resistance of the entire controller | 0.0108 Ohms |
| β | Constant component of the switching loss (per unit of bus voltage) | 0.018153 |
| α | Linear component of the switching loss (per unit of bus voltage) | 0.003345 |
| Cfeq | Equivalent capacitance*frequency of the controller | 0.00015625 |
Using an approximated value of Pmax for the entire car as 9kW, including mechanical and non-controller electrical losses, the per motor controller peak power is 4.5kW. Meaning the approximated output current will vary between 29.8A - 45A (Nominal 34.7A)
From this we can plot the efficiency of the motor controllers versus the voltage and the current using Desmos.
https://www.desmos.com/calculator/kwklxrs8g3
From this plot we can clearly see as power increases the optimal voltage also increases. This optimal voltage range lies in our battery bus range and as such should be relatively optimized to minimize motor controller power losses.
From here we must define the max average temperature and the required flow requirements. This is governed approximately by the following equation.
For more detailed information see the linked data sheet:
https://drive.google.com/file/d/1XMdPXyh2Yv-zCBCM8KNiVlM04B9diN-6/view?usp=sharing