Safety Circuit Fault (Input Open)

What does Safety circuit fault mean?

This fault occurs when the safety circuit input terminals (across S1 and PC, or across S2 and PC) are detected as open. This indicates a break in the safety loop, signaling a potentially unsafe condition and leading to inverter shutdown. It could be due to incorrect wiring, a fault in an external safety device, or an activated safety interlock.

• Emergency Stop button released or pressed incorrectly, causing its NC contact to open the safety loop.
• External safety relay contacts (connected in series to S1/PC or S2/PC) failed to close or opened unexpectedly.
• Guard interlock switch opened due to a door or access panel being unsecured, breaking the safety circuit.
• Broken wire, loose terminal connection, or damaged cable in the external safety circuit loop.
• Faulty external safety device (e.g., light curtain, safety scanner) signaling a trip condition.

Click steps to track your progress.

1. 1

   Verify all emergency stop buttons are released and their associated NC contacts are closed (measure continuity across contacts).

2. 2

   Confirm all safety guard doors and access panels are securely closed, actuating their interlock switches.

3. 3

   Inspect the external safety relay (if present) for proper coil energization and contact closure (measure voltage across coil).

4. 4

   Measure continuity across inverter terminals S1 and PC, and S2 and PC to identify the specific open circuit segment.

5. 5

   Check the status indicators on any connected external safety devices for active alarms or tripped states.

6. 6

   Verify that the safety circuit wiring uses appropriate wire gauge and shielding (e.g., 18AWG twisted pair).