The main control board needs to receive and process various signals from the keyboard and external control circuits, such as modifying parameters, forward and reverse instructions, etc. It also needs to accept and process various internal sampling signals, such as voltage, current, temperature, etc., and generate corresponding control commands based on these signals. Additionally, the main control board can perform SPWM modulation, judge and calculate the received signals comprehensively, generate corresponding SPWM modulation commands, and distribute them to the drive circuits of each inverter tube. In the event of an abnormality, the main control board will immediately issue a protection command for protection or shutdown and output a fault signal. In the frequency converter, the main control board is responsible for receiving and processing various input signals. The main control board will immediately take protective measures.