Motor drive protection – overcurrent, fault handling & testing

What we do

We design fast, reliable protection for motor drives so that faults turn into controlled events instead of destroyed hardware. From overcurrent and short circuits to over- and undervoltage, thermal stress, desaturation and stall conditions, we implement hardware-first shutdown paths with firmware fallback, clear fault handling and repeatable test procedures.

Outcomes we aim for

• Sub-microsecond hardware shutdown for shoot-through and desaturation, followed by deterministic firmware reactions.
• Stable fault state machine with clear diagnostics and well-defined modes such as latched, auto-retry or limp.
• Fewer field failures through SOA-aware limits, thermal derating and EMC-robust measurement chains.
• Documented acceptance criteria and traceable test evidence.

Services

• Protection architecture – split between hardware (gate drivers, DESAT, comparators, BKIN) and firmware (ADC watchdogs, timers) including safe states and restart behaviour.
• Overcurrent and short-circuit protection – DESAT networks, blanking, soft shutdown, shunt / Hall / LEM sizing, Rogowski options and fast paths into TIM BKIN / BRK.
• Over- and undervoltage, brown-out – DC-link sensing, surge filtering, crowbar / bleed strategy, firmware derating and BOR thresholds.
• Thermal and SOA management – junction / case / board sensing, simple thermal models, foldback, cool-down timers, fan and pump control.
• Observer and stall protection – loss-of-sync detection for sensorless drives, speed / position plausibility checks, stall detection and torque limiting.
• Firmware fault handling – fault latching, debounce, time-stamping, error codes, Safe Torque Off (STO) interface where present.
• EMC / ESD robustness – filtering, grounding and shielding, comparator hysteresis, Schmitt inputs and digital filtering with phase awareness.
• Test planning and fixtures – repeatable short-test procedures, overload and brown-out scenarios, thermal ramps, HIL / SIL scripts and logging.
• Design review – gate-driver choice, Miller clamp and deadtime settings, snubber / TVS strategy and layout review including Kelvin shunts and current loops.

Your deliverables

• Protection strategy document (PDF) with block diagrams, thresholds, timing budgets and safe states.
• Schematic and BOM notes for DESAT values, shunt selection, filters and TVS / snubber specifications.
• Firmware module: protection manager for HAL/LL with ISR hooks, ADC watchdogs, state machine and diagnostic events.
• Test plan and reports including procedures, acceptance limits, scope / logic-analyser captures and pass/fail summary.
• Failure tree and lightweight FMEA showing key risks, mitigations and residual risks.
• Handover session (60–90 minutes) with walkthrough for your team.

Technology stack

• Power stages: IGBT / MOSFET inverters, PMSM and BLDC drives, DC, BLAC and induction machines.
• Sensors: shunt, Hall / LEM, Rogowski, NTCs and on-die temperature sensors.
• Gate drivers: DESAT / soft-shutdown, Miller clamp, UVLO and active clamping.
• STM32 features: TIM1 / TIM8 BKIN / BRK kill inputs, deadtime / BDTR, ADC analog watchdog, VREFINT monitoring, COMP / OPAMP, DFSDM, BOR / PVD.
• Standards alignment: supporting customer processes towards IEC / UL / EN (for example ISO 13849 concepts and STO interfaces) on a best-effort basis.

We do not issue certifications; we provide evidence and design work that support your chosen certification path.

Engagement flow

• Discovery (30 minutes) – topology, power levels, fault history and KPIs.
• Architecture and plan – protection tree, thresholds, timings and test list.
• Implementation – hardware values, firmware modules, state machine and logging.
• Validation – bench and HIL tests, corner cases and EMC stress tests.
• Handover – reports, parameter sets, training and proposed next steps.

What we need from you

• Schematics and PCB data for power and control, gate-driver part numbers and shunt / gain details.
• Motor and inverter ratings (DC-link voltage, current, switching frequency) and thermal limits.
• Control stack (MCSDK / HAL / LL), current-measurement method and PWM mode.
• Safety goals such as maximum fault energy, shutdown time and retry policy.

Example packages

• Protection audit (1–2 weeks) – risk review, thresholds and timing budgets, plus a concrete fix plan.
• Implementation sprint (2–4 weeks) – hardware values, firmware manager and initial tests.
• Production hardening – abuse tests, EMC robustness, documentation and training.

Example use cases

• E-mobility inverters – DESAT and BKIN hard-kill with soft-shutdown and controlled restart.
• Pumps and compressors – brown-out ride-through with current and torque foldback.
• Robotics and AGVs – overload protection with thermal derating and safe limp mode.
• Fans and HVAC – acoustically friendly current limiting and restart strategies.

FAQ