A Current Affair: EMRAX 228 Dynanometer Testing

In late March, our electric powertrain section had its first opportunity to run the EMRAX 228 motor on Monash University’s 220Nm Eddy Current Dynamometer using mains power. This gave us a chance to familiarise ourselves with the running of the motor before full power performance testing in the coming weeks using the electric car’s new accumulator.

Performance testing and optimisation is the main reason we put our motor under loading. The dynamometer gives us insight to how the motor will behave under different track conditions. It also facilitates better monitoring and understanding of how the tractive system, which powers the driveline, behaves when assembled. If you would like to learn more about the dynamometers and testing for the combustion powertrain, you can find an article discussing this further here.

Unlike its combustion powered counterpart, the EMRAX does not require tuning variables such as ignition timing and air to fuel ratios. Instead however, the electrical team has been focussing on variables such as torque input and PID controller parameters which influence throttle response. The key reasons for tuning the electric car is keeping the system as efficient and responsive as possible, while striking a balance between electrical trade-offs (such as field weakening and operating temperature) and performance.

Feedback from our components is also measured, such as the temperatures of the motor, inverter and accumulator, and the amount of charge left in each of the cells. These factors will impact the performance, safety, and runtime of the car out on track, and therefore must be closely monitored.

The construction of the accumulator is still in progress, so the preliminary runs of the motor were powered by a DC power supply kindly supplied by the Monash ECSE Department. The supply was only able to provide 20kW of DC power, less than a fifth of the expected power output from our accumulator. This was delivered to the inverter, which converts the DC current from the batteries to 3-phase AC for the EMRAX 228 motor. This alternative allowed us to start mapping the efficiency of the powertrain at low power, through varying voltage and RPM under different loads, as we try to find the optimum torque response. This provided a strong starting point for testing before the completion of the accumulator.
Overall it was a successful preliminary test for the electric powertrain, however, it would not have been possible without the generous support from Monash University and valued long standing sponsor, Treotham. Thank you to the Department of Mechanical and Aerospace Engineering for the use of their dynamometer, the ECSE Department, and Treotham who provided our high voltage cable. The team is looking forward to running the complete system in the very near future.