Title: Inverter and Motor Control Safety | ISO 26262 Academy URL: https://iso26262.academy/features/concepts/inverter-motor-control-safety Description: How a traction inverter earns its ASIL: unintended-torque hazards, Active Short Circuit vs freewheeling safe states, three-level torque monitoring, and the protection layers from gate driver to control software. --- Concept guide · ISO 26262-4/-5 · 12 chapters # Inverter and Motor Control Safety How a traction inverter earns its ASIL: torque hazards, speed-dependent safe states, three-level monitoring, and the protection layers from gate driver to software. 12 Chapters 3 Monitoring Levels 2 Safe States 1 Worked Decomposition Included in Expert [Start learning](https://iso26262.academy/register?plan=free&from=%2Fconcepts%2Finverter-motor-control-safety&utm_source=website&utm_medium=cta&utm_campaign=features_concepts) See the chapters Inside the course 1. 01 **The Torque Machine** 2. 02 **Hazards and Safety Goals** 3. 03 **Inside the Inverter** 4. 04 **Safe States: ASC vs Freewheeling** 5. 05 **The Torque Monitoring Concept** The short version ## Quick answers What makes a traction inverter safety-critical under ISO 26262? The traction inverter converts DC battery power into the phase currents that create motor torque, which makes it the direct controller of the most safety-relevant quantity in an electric vehicle. A malfunction can produce unintended acceleration, unintended braking torque, or loss of propulsion - and unlike a combustion powertrain there is no mechanical linkage or idle behavior to fall back on. Safety goals are typically expressed as limits on torque impulse with a fault tolerant time interval, and the whole chain from accelerator pedal to phase current inherits the resulting ASIL, developed under ISO 26262 Parts 4 and 5. What is Active Short Circuit and when is it the right safe state? Active Short Circuit (ASC) closes all high-side or all low-side switches of the bridge, shorting the machine phases so a spinning permanent-magnet machine circulates current instead of feeding energy back. At high speed it is usually the right safe state for permanent-magnet drives, because opening all switches (freewheeling) would rectify the back-EMF into the DC link and create braking torque plus overvoltage. At low speed the trade-off reverses. The course derives this from the machine physics and covers the high-side vs low-side decision and the machine-type matrix. Keep going, free - [Demo exam · no account Test yourself with 7 exam-style questions](https://iso26262.academy/demo-exam) Why this course · ISO 26262, Part 4 ## Why it pays for itself ### Safe states chosen from physics Above base speed a permanent-magnet machine turns "switch everything off" into a braking event. Learn why safe-state selection is speed-dependent and how the ASC vs freewheeling decision is actually made. ### The monitoring concept OEMs expect The three-level torque monitoring architecture inherited from engine control is the lingua franca of powertrain safety reviews. Learn its levels, its time-budgeted impulse monitors and the sensor plausibility that feeds it. ### Protection across the time scales From desaturation detection in microseconds through fast overcurrent loops to torque monitoring in milliseconds - understand which layer catches which failure and how they compose into one defensible concept. After the course ## What you’ll be able to do ### Derive Torque Safety Goals Work from the malfunction taxonomy of an electric drive to safety goals expressed as torque impulse with an FTTI, the form monitors can actually enforce. ### Select Speed-Dependent Safe States Choose between Active Short Circuit and freewheeling from the machine physics, decide high-side vs low-side ASC, and apply the machine-type matrix. ### Design Three-Level Torque Monitoring Build the pedal-to-current monitoring architecture inherited from engine control, with time-budgeted torque impulse monitors that match the safety goals. ### Keep Sensors and Gate Drivers Honest Specify plausibility for resolver, current, voltage and temperature sensing, and use desaturation detection, soft turn-off and driver self-supervision on the power stage. ### Architect and Decompose the Inverter Apply the recurring architecture patterns, run an ASIL decomposition, set hardware metric targets, and plan degradation strategies. ### Verify the Safety Concept Climb the test environment ladder, inject faults at signal and power level, and prove safe-state entry and FTTI compliance with measurements. The curriculum · 12 chapters ## Chapter by chapter 1. 01 **The Torque Machine** What a traction inverter is, why it controls the single most safety-relevant quantity in an electric vehicle, and why the classic mechanical fallbacks are gone. - Pedal-to-phase chain - Torque as the hazard - No mechanical fallback 2. 02 **Hazards and Safety Goals** The malfunction taxonomy of an electric drive, the HARA logic behind unintended-torque hazards, and safety goals expressed as torque impulse with an FTTI. - Malfunction taxonomy - HARA logic - Torque impulse goals 3. 03 **Inside the Inverter** The B6 bridge anatomy and the role of every subsystem - DC link, power stage, gate drivers, sensing, control board - plus the failure modes that feed later safety analyses. - B6 bridge anatomy - Subsystem roles - Failure modes 4. 04 **Safe States: ASC vs Freewheeling** The physics that makes safe-state selection speed-dependent for permanent-magnet machines, the high-side vs low-side ASC decision, and the machine-type matrix. - Speed-dependent choice - High vs low-side ASC - Machine-type matrix 5. 05 **The Torque Monitoring Concept** The pedal-to-current torque path, the three-level monitoring architecture inherited from engine control, and time-budgeted torque impulse monitors. - Three-level architecture - Torque path - Impulse monitors 6. 06 **Sensor Integrity** Rotor position, phase current, voltage and temperature sensing: the plausibility mechanisms that keep the torque monitor honest when its own inputs fail. - Resolver plausibility - Current-sensor checks - Honest monitor inputs 7. 07 **Gate Drivers and Power-Stage Protection** The safety functions living on the isolation barrier: desaturation detection, soft turn-off, Miller clamping and gate-driver self-supervision. - Desaturation detection - Soft turn-off - Miller clamping 8. 08 **Fast Protection Loops** Overcurrent, DC link overvoltage and overtemperature: the protection layers that live between the microseconds of the gate driver and the milliseconds of the torque monitor. - Overcurrent - DC link overvoltage - Time-scale ladder 9. 09 **Software and Control-Path Safety** The field-oriented control loop as safety-relevant software: protected torque requests with E2E, a trustworthy compute platform, and an unforgeable PWM path. - FOC as safety software - E2E-protected requests - Unforgeable PWM path 10. 10 **Architectures and Decomposition** The recurring inverter safety architectures, a worked ASIL decomposition, hardware metric targets, and the degradation strategies real programs use. - Architecture patterns - Worked decomposition - Degradation strategies 11. 11 **Verifying an Inverter Safety Concept** The test environment ladder, fault injection at signal and power level, proving safe states and the FTTI, and exercising the latent-fault story. - Test environment ladder - Power-level fault injection - FTTI proof 12. 12 **Pitfalls, Trends and Checklist** The failure patterns of real inverter programs, where the technology is heading, and an interactive design review checklist to close the course. - Program failure patterns - Technology trends - Review checklist Diagrams ## Not just text: the visual toolkit ### Machine-Type Safe-State Matrix Which safe state fits which machine type and speed range, and why the answer flips for permanent-magnet machines. ### Protection Time-Scale Ladder From the microseconds of desaturation detection through fast protection loops to the milliseconds of torque monitoring. ### Design Review Checklist An interactive checklist covering the recurring pitfalls of inverter safety programs. Built for ## Who this guide is for - Power electronics engineers moving into safety-rated traction inverters - Functional safety engineers assigned to an e-powertrain item for the first time - Motor control software developers whose control loop just became safety-relevant - System architects decomposing torque-path ASILs across ECU, gate driver and sensors ## Frequently Asked Questions Common questions about Inverter and Motor Control Safety Level 1 is the functional control itself: pedal interpretation, torque arbitration and field-oriented control. Level 2 independently monitors that the delivered torque matches the driver request, typically integrating torque error over time as an impulse monitor with a time budget tied to the FTTI. Level 3 supervises the compute platform itself - the classic architecture inherited from engine control. The monitor is only as honest as its inputs, which is why the course pairs it with resolver, current, voltage and temperature plausibility. Gate drivers sit on the isolation barrier and host the fastest protection in the system: desaturation detection spots a shorted or overloaded switch within microseconds, soft turn-off removes it without a destructive voltage spike, and Miller clamping prevents parasitic turn-on. They also execute the safe-state command - ASC or freewheeling - so their own self-supervision and their independence from the failing control path are part of the safety argument. The course has 12 chapters: the torque machine and its hazard taxonomy, safety goals, inverter anatomy, ASC vs freewheeling safe states, the three-level torque monitoring concept, sensor integrity, gate drivers and power-stage protection, fast protection loops, software and control-path safety, architectures with a worked ASIL decomposition, verification with fault injection, and a closing pitfalls and trends chapter with an interactive design review checklist. It is part of the concept library; a free account starts you off, and the Pro and Expert plans unlock more of the library. ## Start the course today A free account unlocks one full concept guide, 3 work product templates, 1 guided process, the Markov simulator, and 5 practice exams per month. The Pro and Expert plans unlock more of the 78-guide library. No credit card required. [Start learning](https://iso26262.academy/register?plan=free&from=%2Fconcepts%2Finverter-motor-control-safety&utm_source=website&utm_medium=cta&utm_campaign=features_concepts) [View Pricing Plans](https://iso26262.academy/pricing)