The Sevcon Gen 4 controller is a compact, high‑power AC motor driver designed for 3‑phase induction and PMAC motors in battery‑powered traction or pump applications, typically operating up to 540 A RMS at 48 V. Common failure points include over‑temperature shutdowns from inadequate cooling, insulation breakdown between phase windings, CAN bus communication errors with the BMS/VCU, and power supply faults such as undervoltage or ripple on the 48 V rail. First‑check diagnostics should verify the 48 V input voltage and ripple with an oscilloscope, inspect all phase winding connections for continuity and insulation resistance, and review the controller’s fault log via CAN or the onboard display for any error codes indicating overcurrent, overheating, or communication loss.[oss-gpt-20b]