To deliver high voltage electrical power from the accumulator to the motor safely, and to shut that path down reliably whenever the rules or a fault require it.
Power flows from the accumulator through the accumulator isolation relays, past the precharge circuit, through EMI-shielded HV cable to the DTI HV-550 motor controller, and into an EMRAX 228 LV motor with a custom winding. A Tamagawa TS2620N21E11 resolver gives the inverter rotor position. The interlock circuit runs in series through every shutdown button, the inertia switch, the brake plausibility device and the insulation monitoring device; opening it anywhere drops the contactors and de-energises the tractive system. The miscellaneous circuits are the rules-mandated indicators: tractive system status indicator, voltage indicator, ready-to-move light and the ready-to-drive sound. The motor controller runs in torque control mode with regenerative braking capability, hardware and software overvoltage and overcurrent protection, power stage and motor temperature limiting, and presets for EMRAX motors.
Reliability, safety and rules compliance before performance. This is a first-year EV program, and the tractive system is where scrutineering failures happen. Fix the failure mode, not the symptom. Four specific upgrades were adopted against four specific observed problems: star grounding against CAN dropouts and resets from HV noise; contactor AUX feedback against contactors that give no reliable state feedback (without it the tractive system could stay energised while the shutdown circuit believes it is off); EMI-shielded HV cable against signal integrity loss; flat braid lugs and deliberate routing against connections loosening or overheating under load. 1. Select the motor against the available options. EMRAX is effectively the only viable choice for a non-in-hub design; the 228 LV+43% keeps the 111 kW peak power of the 228 MV at a lower maximum operating voltage. 2. Select the controller against the motor. The PM100DX was chosen first, then discontinued; the recommended CM200DX was lighter and more powerful, but Cascadia does not support the EMRAX custom windings, which is what moved the team to the DTI HV-550 (30-800 VDC, 280 A max input, 320 kW max output, 95% efficiency, 6.8 kg). 3. Draw the tractive system diagram and the interlock chain, then place every component against it. 4. Choose cable and insulation for routing as well as rating. CoreFlex HV cable was chosen because it is far more flexible than standard HV wire, making routing inside the accumulator easier and cleaner, with thick insulation that helps at scrutineering. Nomex YT510 was chosen for safety barriers inside the container. 5. Bench test the shutdown chain before the pack is live.
- Increase tractive system reliability by reducing electrical noise, improving feedback and isolating failure points. - Improve serviceability for inspection and maintenance. - Get the car moving. - Pass the tractive system master switch safety checks with contactor AUX feedback.
- High voltage noise interfering with low voltage sensors, seen as CAN dropout and resets. - Contactors providing no reliable state feedback. Mechanical wear or bounce can give inconsistent readings on budget contactors. - Cable connections loosening or overheating under load. - Scrutineering findings on unclear grounding, shielding and cable layout.
Tractive system block diagrams. Vendor datasheets for motor, controller and resolver. Bench validation of the interlock chain. The FSAE EV ruleset (EV.5.2 motor controller, T.5.3 motor protection) as the primary design constraint.