In a 3-wire PLC-controlled VFD system, PLC outputs must be connected to at least how many VFD input(s)?

In a 3-wire PLC-controlled Variable Frequency Drive (VFD) system, the PLC outputs must be connected to at least two VFD inputs to effectively control the operation of the motor.

The primary purpose of this configuration is to enable the PLC to provide both start/stop commands and directional control to the VFD. Typically, one output from the PLC is used to initiate the start of the motor, while the second output is employed to set the motor's direction of rotation (either forward or reverse). This dual input setup ensures that the VFD can respond accurately to both the operational and directional commands issued by the PLC.

A single input connection would not suffice, as it would not allow for the flexibility necessary to control both starting/stopping and directional functions. Thus, having at least two inputs connects the PLC's functions with the control capabilities of the VFD, thereby ensuring efficient operation in automation scenarios.