Feedback braking converts the motor's renewable electricity into AC electricity back to the grid at the same frequency as the grid through active reversal technology to achieve energy recovery. Its core is:
Voltage detection: triggers feedback when the DC bus voltage exceeds 1.2 times the effective value of the grid voltage (such as 400V systems up to 678V).
Synchronous control: It is necessary to accurately detect the grid frequency and phase (error < 1 °) to ensure that the feedback current is synchronized with the grid.
Current Limitation: Control the feedback current through PWM modulation to avoid overcurrent causing grid pollution (THD < 5%).
Technical classification and application scenarios
Type Implementation Application Scenario
DC Feedback Reverse Coupling Diode Straightening, Feedback to DC Motherboard DC Motor, Electric Locomotive
AC Feedback Full Bridge Inverter + LC Filter, Feedback to AC Grid Asynchronous Motor, High Power Frequency Converter
Mixed feedback combined with energy storage devices (e.g. supercapacitors) to buffer energy grid instability or off-grid systems
Key performance indicators
Efficiency: typical feedback efficiency ≥95%, high power system (> 100kW) can reach 97%.
Response time: Delay <10ms from detection to overvoltage to start-up feedback.
Harmonic suppression: Meet IEC 61000-3-2 standard (THD < 5%).
Typical Application Scenarios
Large inertial load: such as centrifuges, rolling mills, renewable energy when braking can reach 30% of the rated power of the motor.
Bit energy load: when the elevator or crane falls, the gravitational potential is converted into electrical energy back to the grid.
Fast braking: machine tool spindle braking time is reduced by more than 50%.
Selection and Considerations
Grid compatibility: Grid voltage fluctuations should be ≤15%, otherwise it may damage the device.
Heat dissipation design: IGBT junction temperature needs <125 ℃, forced air cooling when wind speed ≥2m / s.
Protection function: overvoltage / overcurrent protection threshold needs to be adjustable (e.g. 1.2 times the grid voltage).
Comparison with other braking modes
Braking mode Energy handling Disadvantages of application scenario
Energy consumption Brake resistance heat consumption Medium and small power, low frequency braking efficiency, severe heating
Feedback Brake Power Feedback Grid High power, frequent braking control complex, high cost
DC Brake Stator Pass DC Electric Brake Precise Parking, Low Speed Brake For Short Time Use Only