The next post in this blog series introduces the Powertrain module. It is responsible for the development, production and maintenance of the inverters.
Two inverters are installed in the all-wheel drive EDGE, with each inverter controlling two of the permanent magnet synchronous motors, which is a special type of electric motor. Essentially, the inverter converts the direct current (DC) from the 600 V battery into three-phase AC voltage for the motors.
The hardware for the inverter essentially consists of a controller, twelve gate drivers and six silicon carbide half bridges, which are an arrangement of two transistors. The controller generates a signal for the gate drivers which directly switch the transistors of the half bridges. Supported by the DC link capacitors, the half bridges switch the energy from the battery. The inverter also contains hardware protection circuits to deactivate the controller in the event of overcurrent or overvoltage, or in case of gate driver faults. As switching frequencies of 20 kHz can cause interference, an EMI filter is also featured in the inverter. It ensures that interferences do not travel out of the inverter via the supply line and thus influences other components.
The required circuit boards are developed by Powertrain using KiCad. The members write code for the Texas Instruments controller in the C programming language using the Code Composer Studio. It receives the desired torque from the ECU via the CAN bus, the communication system in the car, and sets this as input variable for the field-orientated control. This control loop ensures that the requested torque is converted into signals for the gate drivers. Part of this control is also a rotary encoder on the motor (in our case a resolver) and current sensors on each phase.
The module members use MATLAB/Simulink to create a digital model of the inverter. This can be used to simulate various switching patterns for the gate drivers, which can be optimized for efficiency or performance, for example. In order to test and validate new components or modified software in the inverter, Powertrain has access to an inverter and motor test bench at TU Wien.
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