When the motor decelerates, the regenerated energy cannot be effectively released (i.e., the regenerated energy is trapped in the system), which can lead to an abnormal increase in DC bus voltage, causing a series of chain problems. In severe cases, it may damage the driver, motor, or even the entire control system. The specific consequences are as follows: 1 When the overvoltage alarm of the drive (the most direct consequence) fails to release the regenerated energy, the electric energy generated by the motor as a generator will be fed back to the DC bus of the drive (such as the DC link of the frequency converter and servo drive) in reverse, causing a sharp increase in bus voltage. When the voltage exceeds the "overvoltage protection threshold" set by the driver (such as a 380V input driver, which usually triggers protection when the bus voltage exceeds 700V), the driver will immediately report an "overvoltage fault" (such as Yaskawa's "OV", Siemens' "F0002") and shut down, interrupting the production process. two Damage to power devices (hardware level risk): If overvoltage protection fails (such as protection circuit failure) or the voltage rise speed exceeds the protection response time, excessive DC bus voltage will breakdown the power semiconductor devices inside the driver, such as IGBT modules and rectifier bridges, causing device short circuits or permanent damage; The filtering capacitor on the DC bus may swell, leak or even explode due to overvoltage (the withstand voltage value of electrolytic capacitors is usually 1.2-1.5 times the rated voltage of the bus, and they are prone to failure after overvoltage). three During abnormal or damaged motor operation and deceleration process, the retention of regenerative energy can cause the reverse voltage at both ends of the motor to rise, which may break through the insulation layer of the motor winding (especially during high-frequency regeneration) and cause inter turn short circuits; If the drive is frequently shut down and restarted due to overvoltage, the motor may be subjected to frequent current surges, resulting in overheating of the windings, increased bearing wear, and shortened service life. four Even if the overvoltage alarm is not triggered, abnormal fluctuations in bus voltage can interfere with the control circuit of the driver (such as current detection and pulse output modules), leading to shaking, speed overshoot, or inaccurate positioning of the motor during deceleration (such as increased servo motor stop error); The fluctuating voltage may be transmitted to other devices (such as PLCs, sensors) through the power circuit, causing cascading failures such as communication interference and data errors. five If the braking unit/resistor is overloaded and damaged (if not configured properly), and the system is already equipped with a braking unit or resistor, but the regenerative energy cannot be fully consumed due to small selection, loose wiring, or aging of the resistor, it can cause overheating of the braking resistor (exceeding the rated power), burning of the insulation layer, and even causing a fire; The power tube inside the braking unit is damaged due to long-term overcurrent, further losing the energy release path and exacerbating the risk of overvoltage. The core hazard of the inability to release regenerative energy during motor deceleration is DC bus overvoltage, which can have consequences ranging from "system shutdown" to "hardware burnout", especially in scenarios of rapid deceleration, high inertia loads (such as machine tool spindles, elevators), or frequent start stop. To solve the problem, it is necessary to ensure timely consumption or recovery of regenerative energy through reasonable configuration of braking resistors/braking units, extension of deceleration time, and use of energy feedback devices.