nErr Commercial Power Switching Error fault in Toshiba drive
nErr Commercial Power Switching Error fault in Toshiba drive
Description This fault is specific to applications using a "Bypass" setup, where the motor can be driven by the VFD *or* directly by the utility grid (Commercial Power). The "nErr" indicates a failure during the transition. For example, if the drive commands the Bypass Contactor to close but detects that the VFD Output Contactor is still closed, it trips nErr to prevent feeding utility power backwards into the VFD output (which would cause an explosion). Causes
1. Stuck Contactor: The output contactor (between VFD and Motor) is welded shut.
2. Interlock Failure: The mechanical or electrical interlock between the VFD contactor and Bypass contactor is broken.
3. Timing: The "Switching Delay" parameter is too short, not allowing enough time for the arc to extinguish in one contactor before the other closes.
4. Feedback Wiring: The auxiliary contact telling the drive the status of the bypass is wired incorrectly. Solution Inspect the external contactor panel. Manually depress the contactors (with power off) to ensure they move freely and are not welded.
Check the "Answer" input. The drive usually requires a digital input to confirm "Bypass is active." If this signal is missing or arrives too late, nErr triggers.
If you are NOT using a bypass but getting this error, check the "Commercial Power Switching" parameter (often F354). Ensure it is set to "Disable." If enabled without the proper external circuitry, the drive will trip expecting feedback that doesn't exist.
Description This fault is specific to applications using a "Bypass" setup, where the motor can be driven by the VFD *or* directly by the utility grid (Commercial Power). The "nErr" indicates a failure during the transition. For example, if the drive commands the Bypass Contactor to close but detects that the VFD Output Contactor is still closed, it trips nErr to prevent feeding utility power backwards into the VFD output (which would cause an explosion). Causes
1. Stuck Contactor: The output contactor (between VFD and Motor) is welded shut.
2. Interlock Failure: The mechanical or electrical interlock between the VFD contactor and Bypass contactor is broken.
3. Timing: The "Switching Delay" parameter is too short, not allowing enough time for the arc to extinguish in one contactor before the other closes.
4. Feedback Wiring: The auxiliary contact telling the drive the status of the bypass is wired incorrectly. Solution Inspect the external contactor panel. Manually depress the contactors (with power off) to ensure they move freely and are not welded.
Check the "Answer" input. The drive usually requires a digital input to confirm "Bypass is active." If this signal is missing or arrives too late, nErr triggers.
If you are NOT using a bypass but getting this error, check the "Commercial Power Switching" parameter (often F354). Ensure it is set to "Disable." If enabled without the proper external circuitry, the drive will trip expecting feedback that doesn't exist.
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