A:  ① Access control failure: The contact points of the access control switch are broken, or the S3 interface of the system IO board is faulty.
② Overheating of the phase-shifting transformer: The direction of the fan is incorrect, the temperature controller gives a false alarm, or there is too much dust in the environment.
③ Bypass cabinet action failure: The manual/automatic type setting is incorrect, or the address setting is wrong.
④ Buffer cabinet failure: The buffer contactor or the system IO board is faulty.
⑤ Frequency converter overload: The selected model is too small; the grid voltage is too low; the parameter setting is incorrect; the current detection circuit is faulty.