STM32G431KB Motor Control MCU
1kW Variable Frequency Drive
Overview
A reliable 1kW open-frame Variable Frequency Drive powered by the FNB33060T Motion SPM 3, designed for single-phase 220V-240V AC input to control industrial AC induction pumps and fans with local potentiometer and push-button control.
Mohammad Ali JahangiriSystem architecture
POWER
MODULE
MCU
SENSOR
DISPLAY
- EMI_FILTER → RECTIFIER_AND_DC_LINKPowerFiltered AC mains input to bridge rectifier
- RECTIFIER_AND_DC_LINK → SPM_INVERTER_STAGEPowerHigh voltage DC bus power supply
- RECTIFIER_AND_DC_LINK → AUX_POWER_SUPPLYPowerDC bus feeding auxiliary flyback converter
- AUX_POWER_SUPPLY → MOTOR_MCUPowerIsolated/regulated power supply for MCU and logic
- MOTOR_MCU → SPM_INVERTER_STAGEPWMSPM high-side and low-side gate control PWM signals
- CURRENT_SENSING → MOTOR_MCUADCPhase current analog feedback to MCU ADC
- LOCAL_UI → MOTOR_MCUGPIOPotentiometer analog speed reference, push button GPIOs, and display interface
Bill of materials
| Part number | Type | Component | Manufacturer | Package | Qty | Datasheet | Match |
|---|---|---|---|---|---|---|---|
| B32923C3225M | POWER | AC Common-Mode Choke & Film Capacitors Filters conducted electromagnetic interference from the single-phase AC mains. | EPCOS | CAP_26.5X14.5MM_TM | 1 | Matched | |
| GBU8M-E3/45 | POWER | GBU8M Bridge Rectifier & Bulk Electrolytic Capacitors Converts single-phase AC to high-voltage DC bus (~310V-340V) with Pi-filter smoothing. | Vishay General Semiconductor | Tube | 1 | Matched | |
1 alternatives consideredAI verified | |||||||
| FNB33060T | MODULE | onsemi FNB33060T Motion SPM 3 Module Integrates 600V/30A IGBTs, gate drivers, and bootstrap diodes for 3-phase motor drive. | ON SEMICONDUCTOR | 27-PowerDIP Module (1.205", 30.60mm) | 1 | Matched | |
| TOP255GN | POWER | Flyback SMPS (TOPSwitch / TinySwitch) Steps down DC bus voltage to isolated/non-isolated +15V (gate bias) and +3.3V (MCU/logic). | Power Integrations | — | 1 | Pending | |
2 alternatives consideredAI verified | |||||||
| STM32G431KBT6U | MCU | STM32G431KB Motor Control MCU Executes continuous V/Hz control loops, generates high-resolution PWMs, and handles protection trips. | Stmicroelectronics | 32-LQFP | 1 | Matched | |
4 alternatives consideredAI verified | |||||||
| LM358WDT | SENSOR | Low-side Shunt Resistors & Operational Amplifiers (LM358) Measures phase currents via low-ohm shunt resistors on SPM low-side open emitters for feedback and OCP. | ROHM | 8-SOIC (0.154", 3.90mm Width) | 1 | Matched | |
1 alternatives consideredAI verified | |||||||
| TM1637 | DISPLAY | 10kΩ Potentiometer, Tactile Push Buttons & TM1637 Display Provides local user interface for speed adjustment (potentiometer) and start/stop control. | TM | SOP20 | 1 | Matched | |
Build guide
6-8 hoursAdvanced
1
Procurement & Preparation
- Source and inspect the core Bill of Materials including B32923C3225M X2 film capacitors, GBU8M-E3/45 bridge rectifier, FNB33060T Motion SPM 3 module, TOP255GN switcher, STM32G431KBT6U MCU, LM358WDT op-amp, and TM1637 display driver module.
- Prepare the open-frame aluminum baseplate and extruded heatsink, applying a thin, uniform layer of thermal interface material (silicone-free thermal grease) for the FNB33060T SPM module and GBU8M bridge rectifier.
- Pre-program the STM32G431KBT6U microcontroller using an ST-LINK v3 debugger with the initial bootloader and V/Hz firmware binary via SWD pins.
2
Hardware Assembly & Wiring
- Populate and solder the AC Common-Mode Choke, B32923C3225M X2 film capacitors, and GBU8M-E3/45 bridge rectifier onto the AC-DC input section of the open-frame PCB.
- Mount the FNB33060T Motion SPM 3 module and bulk electrolytic capacitors to the PCB and heatsink assembly, securing mounting screws to specified torque.
- Assemble the Flyback SMPS circuit featuring the TOP255GN, transformer, and secondary filter capacitors to generate isolated +15V gate bias and +3.3V logic rails.
- Solder the STM32G431KBT6U MCU, LM358WDT operational amplifiers, low-side current sensing shunt resistors, and interface connectors on the control board.
- Connect the local user interface board containing the 10kΩ potentiometer, start/stop push buttons, and TM1637 display to the main board via the GPIO/ADC wire harness.
3
Firmware Setup
- Configure the motor control parameter header file in the firmware project for a 1kW induction motor (rated voltage 220V, frequency 50Hz/60Hz, 4 poles).
- Compile and flash the complete V/Hz control firmware with space vector PWM generation, dead-time insertion, and overcurrent protection trip routines.
- Calibrate the ADC scaling factors for the low-side shunt current feedback (IU_FB, IV_FB, IW_FB) and potentiometer input (POT_ADC) using the debugging interface.
4
Testing & Calibration
- Perform cold insulation and continuity checks on the input AC terminals and DC bus rails using a digital multimeter and insulation tester.
- Power up the control board via an isolated low-voltage DC supply or variac to verify SMPS output rails (+15V gate drive and +3.3V logic) and TM1637 display initialization.
- Conduct a no-load functional test by applying single-phase 230V AC input, using the potentiometer to adjust speed, and testing the start/stop push buttons while monitoring output phases on an oscilloscope.
- Perform a full-load burn-in test driving a 1kW 3-phase induction motor under load for 30 minutes, monitoring heatsink temperature, PWM switching waveforms, and overcurrent trip response.
Document
1kW Variable Frequency Drive
A reliable 1kW open-frame Variable Frequency Drive powered by the FNB33060T Motion SPM 3, designed for single-phase 220V-240V AC input to control industrial AC induction pumps and fans with local potentiometer and push-button control.
Executive Summary
This reference design defines the system architecture, critical component candidates, risk register, and validation path for 1kW Variable Frequency Drive. It is a system-level design deliverable; verify critical claims with manufacturer evidence and prototype testing before production release.
Design Overview
Requirements Coverage
| Requirement | Architecture coverage | Status |
|---|---|---|
| Single-phase 220V-240V AC to 3-phase AC conversion using FNB33060T Motion SPM 3 | Pending validation | Needs verification |
| Continuous V/Hz control for industrial AC induction motors in pumps and fans | Pending validation | Needs verification |
| Local user interface with potentiometer for speed adjustment and push buttons for start/stop control | Pending validation | Needs verification |
| Open-frame PCB power and control architecture optimized for industrial chassis integration | Pending validation | Needs verification |
| Comprehensive protection including overcurrent, undervoltage, overtemperature, and short-circuit monitoring | Pending validation | Needs verification |
| Item | Details |
|---|---|
| Product Type | 1kW Variable Frequency Drive |
| Key Functions | Single-phase 220V-240V AC to 3-phase AC conversion using FNB33060T Motion SPM 3, Continuous V/Hz control for industrial AC induction motors in pumps and fans, Local user interface with potentiometer for speed adjustment and push buttons for start/stop control, Open-frame PCB power and control architecture optimized for industrial chassis integration, Comprehensive protection including overcurrent, undervoltage, overtemperature, and short-circuit monitoring |
| Power Source | AC 220V-240V |
| Connectivity | Analog Input, Digital GPIO |
| Size | Open-frame PCB design for machine chassis integration |
| Environment | industrial indoor |
| Difficulty | Advanced |
| Est. Time | 6-8 hours |
System Architecture
Power Topology: Single-phase AC input -> EMI Filter -> Rectifier & DC-Link Capacitor Bank (~310V DC Bus) -> Split power branches: (1) FNB33060T SPM Inverter Stage to 3-phase Motor, (2) Flyback SMPS generating +15V (gate bias) and +3.3V (MCU & UI logic).
Module List
| Module ID | Type | Name | Function | Voltage |
|---|---|---|---|---|
| EMI_FILTER | POWER | AC Common-Mode Choke & Film Capacitors | Filters conducted electromagnetic interference from the single-phase AC mains. | 230VAC |
| RECTIFIER_AND_DC_LINK | POWER | GBU8M Bridge Rectifier & Bulk Electrolytic Capacitors | Converts single-phase AC to high-voltage DC bus (~310V-340V) with Pi-filter smoothing. | 310VDC |
| SPM_INVERTER_STAGE | MODULE | onsemi FNB33060T Motion SPM 3 Module | Integrates 600V/30A IGBTs, gate drivers, and bootstrap diodes for 3-phase motor drive. | 310VDC |
| AUX_POWER_SUPPLY | POWER | Flyback SMPS (TOPSwitch / TinySwitch) | Steps down DC bus voltage to isolated/non-isolated +15V (gate bias) and +3.3V (MCU/logic). | 15V |
| MOTOR_MCU | MCU | STM32G431KB Motor Control MCU | Executes continuous V/Hz control loops, generates high-resolution PWMs, and handles protection trips. | 3.3V |
| CURRENT_SENSING | SENSOR | Low-side Shunt Resistors & Operational Amplifiers (LM358) | Measures phase currents via low-ohm shunt resistors on SPM low-side open emitters for feedback and OCP. | 3.3V |
| LOCAL_UI | DISPLAY | 10kΩ Potentiometer, Tactile Push Buttons & TM1637 Display | Provides local user interface for speed adjustment (potentiometer) and start/stop control. | 3.3V |
Power Tree and Signal Interfaces
| From | To | Type | Interface / rail | Voltage |
|---|---|---|---|---|
| EMI_FILTER | RECTIFIER_AND_DC_LINK | power | Power | 230VAC |
| RECTIFIER_AND_DC_LINK | SPM_INVERTER_STAGE | power | Power | 310VDC |
| RECTIFIER_AND_DC_LINK | AUX_POWER_SUPPLY | power | Power | 310VDC |
| AUX_POWER_SUPPLY | MOTOR_MCU | power | Power | 3.3V |
| MOTOR_MCU | SPM_INVERTER_STAGE | data | PWM | 3.3V |
| CURRENT_SENSING | MOTOR_MCU | data | ADC | 3.3V |
| LOCAL_UI | MOTOR_MCU | data | GPIO | 3.3V |
Design Schemes
Standard Motion SPM 3 Inverter Architecture for 1kW VFD ★
Single-phase AC to 3-phase DC/AC conversion utilizing the FNB33060T module, driven by an STM32G431 motor control MCU with low-side shunt current sensing and auxiliary flyback power supply.
Trade-offs: Offers high reliability, compact footprint, and optimal thermal performance via direct heatsink mounting, balanced with cost-effectiveness for industrial fan and pump applications.
Key IC selection
main motor control MCU
- Need: Execute real-time V/Hz control algorithms, generate advanced center-aligned PWMs with deadtime insertion, and handle fast OCP trips.
- Class: 32-bit ARM Cortex-M4 mixed-signal microcontroller with high-resolution hardware timers and fast ADCs
- Shortlist: STMicroelectronics STM32G431xx, Microchip dsPIC33CKxx
- Pick: Select based on built-in math accelerators (CORDIC/FMAC), advanced HRTIM peripherals, package availability (LQFP32), and motor control SDK ecosystem maturity.
3-phase intelligent power module
- Need: Drive 1kW induction motor efficiently from a ~340V DC bus with integrated gate driving, bootstrap diodes, and thermal protection.
- Class: 600V Smart Power Module (SPM) / Inverter Power Module combining trench IGBTs and HVIC drivers
- Shortlist: onsemi FNB33060T, STMicroelectronics STGIB30M60TS-L
- Pick: Select based on continuous current rating (>10A RMS for 1kW), thermal resistance, built-in V_CE(SAT) / temperature monitoring, and footprint compatibility.
phase current feedback and protection
- Need: Accurately amplify millivolt-level low-side shunt voltage drops with wide bandwidth and low offset for cycle-by-cycle current feedback.
- Class: Dual low-offset, high-bandwidth operational amplifier suited for single-supply current sensing
- Shortlist: STMicroelectronics LM358APT, Texas Instruments OPA2365
- Pick: Select based on unity-gain bandwidth, slew rate, input common-mode range including ground, and cost optimization for open-frame industrial hardware.
Risk register
| ID | Area | Severity | Detail | Mitigation |
|---|---|---|---|---|
| r1 | thermal | high | The FNB33060T module dissipates significant conduction and switching losses at 1kW output, risking thermal shutdown if heatsinking is inadequate in an open-frame chassis. | Ensure proper thermal interface material (TIM) application, calculate worst-case junction temperature under overloaded V/Hz conditions, and allocate adequate extrusion heatsink area with airflow clearance. |
| r2 | emi | high | High dV/dt (fast switching edges from the SPM IGBTs) combined with open-frame construction can cause conducted and radiated EMI failures violating EN 61800-3. | Optimize PCB layout for minimum loop area on the DC bus and inverter outputs, include snubber networks or gate resistors if needed, and ensure proper grounding of the EMI filter common-mode choke. |
| r3 | power | med | Low-side shunt resistor layout parasitics and high dv/dt switching noise can inject severe common-mode spikes into the LM358 op-amp inputs, causing false OCP trips or erratic V/Hz control. | Use Kelvin connection routing for the shunt resistors, place RC filtering close to the op-amp inputs, and maintain clean separation between power ground and signal ground planes. |
Bring-up and Validation Plan
- Power-off inspection and rail resistance checks
- Current-limited first power-up; verify every rail before enabling loads
- Validate interfaces and timing one subsystem at a time
- Run thermal, fault-injection, EMC pre-scan, and endurance tests for the target environment
Key Components
6/7 modules matched to real parts. See the BOM tab for the full component table.
AC Common-Mode Choke & Film Capacitors (B32923C3225M)
The candidate's MPN (B32923C3225M) exactly matches the primary MPN.
GBU8M Bridge Rectifier & Bulk Electrolytic Capacitors (GBU8M-E3/45)
Candidate 1 (GBU8M) matches the primary MPN directly with the preferred manufacturer designation of 'Multiple'.
Flyback SMPS (TOPSwitch / TinySwitch) (TOP255GN)
Web recommendation: TOP255GN (not in ES)
STM32G431KB Motor Control MCU (STM32G431KBT6U)
The candidate STM32G431KBT6 matches the primary MPN STM32G431KB and correctly identifies STMicroelectronics as the manuf
Build Summary
- Difficulty: Advanced
- Estimated time: 6-8 hours
- Tools required: Temperature-controlled soldering iron, Hot air rework station, Torque screwdriver, Multimeter, Isolated oscilloscope, Differential voltage probes
See the Build tab for the full step-by-step assembly guide.
Evidence and Limitations
- Confirm part parameters, certifications, and compatibility against current manufacturer documents.
- Treat industry compliance without test or certificate evidence as a compliance gap, not an approval.
- See Reference Images for visual artifacts and Build Guide for detailed assembly and bring-up steps.