In general, it is not recommended to connect the contactor at the output end of the converter. If it is necessary to connect the contactor, the following guidelines shall be followed: start, close the contactor first, and then start the converter; stop, stop the converter first, and then disconnect the contactor. It is absolutely not allowed to cut in or disconnect the contactor suddenly when the frequency converter is running, because it will cause huge impact current, damage the frequency converter or motor, and even cause explosion in serious cases.