E-41Â STO Diagnostic Mismatch fault in Toshiba drive
E-41 STO Diagnostic Mismatch fault in Toshiba drive
Description The Safe Torque Off (STO) circuit is redundant (Dual Channel). E-41 is an internal self-test failure of this safety system. The drive periodically runs a diagnostic where it briefly attempts to toggle the internal safety relays to ensure they are not welded shut. If the result of this test is illogical (e.g., the relay signals it is closed when it should be open), the drive locks down in E-41. This is a higher-level fault than E-30 (which is external wiring). Causes
1. Internal Component Failure: The optocouplers or safety relays on the control board have degraded.
2. Voltage Sag: The 24VDC supply dipped during the self-test diagnostic pulse.
3. Noise Spikes: EMI caused a bit-flip in the safety processor logic. Solution This fault latches hard. You must perform a full power cycle. Turn off the mains, wait for the display to go completely black, wait another 30 seconds, then power on.
If E-41 returns immediately, there is likely a hardware failure on the VFD's safety circuit. Because this is a life-safety critical circuit, it is not user-serviceable. You cannot bypass it or repair it with a soldering iron without voiding safety certifications (SIL3/PLe). The drive or control board must be replaced.
Ensure your external 24V power supply (if used for STO) is stable and can handle the inrush current of the safety circuit.
Description The Safe Torque Off (STO) circuit is redundant (Dual Channel). E-41 is an internal self-test failure of this safety system. The drive periodically runs a diagnostic where it briefly attempts to toggle the internal safety relays to ensure they are not welded shut. If the result of this test is illogical (e.g., the relay signals it is closed when it should be open), the drive locks down in E-41. This is a higher-level fault than E-30 (which is external wiring). Causes
1. Internal Component Failure: The optocouplers or safety relays on the control board have degraded.
2. Voltage Sag: The 24VDC supply dipped during the self-test diagnostic pulse.
3. Noise Spikes: EMI caused a bit-flip in the safety processor logic. Solution This fault latches hard. You must perform a full power cycle. Turn off the mains, wait for the display to go completely black, wait another 30 seconds, then power on.
If E-41 returns immediately, there is likely a hardware failure on the VFD's safety circuit. Because this is a life-safety critical circuit, it is not user-serviceable. You cannot bypass it or repair it with a soldering iron without voiding safety certifications (SIL3/PLe). The drive or control board must be replaced.
Ensure your external 24V power supply (if used for STO) is stable and can handle the inrush current of the safety circuit.
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