Quick switching of the frequency converter speed control mode

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Fast switching between variable frequency drive speed control modes: Large-scale production facilities have a high level of automation; under normal conditions, the starting, stopping, and speed regulation of their motors are controlled by the DCS system. However, in the event of an accident in the production facility, especially one involving the DCS system, manual operation becomes necessary. This requires that the variable frequency speed control system be able to switch quickly between manual and automatic modes. The attached diagram shows the control system designed using the Fuji FBEP41C5000G9S series inverter as an example. The switching between the manual operating system and the DCS operating system is achieved by the transfer switch SA, which is installed on the field control panel and has three modes: automatic, manual, and stop. When the switch is in the manual position, pressing button SST causes the contactor K to close, and the frequency converter U is powered on. At this point, U should be set to panel key operation mode; it is started and stopped using the RUN and STOP buttons, while speed control is achieved using the V button ； When the changeover switch SA is in the stop position, K loses power and U is in a powered-off state ； When SA is set to the automatic position, the intermediate relay KM becomes energized; its auxiliary contacts connect the U terminal X4—CM to the FWD—CM terminal. The former forces U to operate in a state where the current input signal is valid, while the latter enables U to rotate in the forward direction. At this point, U receives a 4–20mA speed control signal from the DCS system in order to regulate its speed, and panel operations are ineffective. Thus, the control state transition of U is completed.