Simultaneous Forward/Reverse Command or Digital Input Triggered

What does External Fault mean?

This fault can occur due to two distinct conditions: either a forward and reverse command were simultaneously active for over 500ms, indicating a control signal conflict; or an external device triggered a fault via one of the digital inputs (S1-S6), pointing to an issue in an external safety or interlock circuit. Both scenarios lead to motor stoppage and require careful investigation of control logic and external devices.

• Simultaneous activation of both Forward and Reverse digital input commands (e.g., S1 and S2) for more than 500ms due to PLC logic error or faulty control switch.
• External fault input (e.g., H1-0x = 2 for 'External Fault') configured on a digital input terminal (e.g., S4) is activated by an external safety device or sensor.
• Wiring short between a Run command input (e.g., S1) and a digital input configured as an External Fault (e.g., S4) or between FWD/REV commands.
• Faulty relay or contactor providing control signals, causing momentary or continuous simultaneous Forward/Reverse signals.
• Incorrectly configured external fault input (e.g., active high instead of active low) in parameters (e.g., H1-0x).

Click steps to track your progress.

1. 1

   1. Check the drive's input status monitor (e.g., U1-01) to identify which digital inputs are active. Confirm that Forward and Reverse command inputs (e.g., S1 and S2) are not simultaneously 'on'.

2. 2

   2. If an external fault input is configured (e.g., H1-04 for S4 = 2 'External Fault'), check the state of the physical terminal (e.g., S4) and the external device connected to it (e.g., measure 24VDC).

3. 3

   3. Review PLC or control logic for simultaneous activation of Forward/Reverse commands, especially during transitions or error states.

4. 4

   4. Inspect all wiring from the control system to the drive's digital input terminals (e.g., S1, S2, S4) for shorts, loose connections, or incorrect terminations.

5. 5

   5. Temporarily disable the external fault function (e.g., set H1-0x to 'Not Used') if it is suspected to be a false trigger, then re-enable after troubleshooting the external device.