A: In the process of deceleration or stop of the inverter, due to the set deceleration time is too short or the braking capacity is not enough, the bus voltage inside the inverter is increased and protection (also known as overvoltage stall) occurs. As a result, the inverter loses the speed control of the motor. At this time, a long deceleration time should be set to keep the bus voltage in the transformer from rising too high to realize normal deceleration control. In the process of increasing speed of inverter, the set acceleration time is too short or the load is too heavy, and the grid voltage is too low, which leads to the converter over-current and protection (also known as over-current stall). When the inverter loses the speed control of the motor, a longer speed up time should be set to maintain no over-current and realize normal speed-up control.