FL Error FL Relay / Safety Output fault in Toshiba drive
FL Error FL Relay / Safety Output Fault fault in Toshiba drive
Description The "FL" terminals (FLA, FLB, FLC) are the main fault relay outputs of the drive. In some high-spec Toshiba drives (like G9/AS3), the drive monitors the status of this relay. If the CPU commands the relay to close, but the internal feedback detects it didn't close (or welded shut), it generates an FL system error. This ensures that if the drive faults, the external world (alarms/contactors) is reliably notified. Causes
1. Welded Contacts: The relay contacts have fused together because the user connected a high-current load (like a large solenoid) without a suppression diode.
2. Mechanical Failure: The relay mechanism is broken due to vibration or age.
3. External Voltage Backfeed: High voltage was accidentally applied to the FL terminals, damaging the monitoring circuit. Solution This is a hardware failure indication.
Listen to the drive during power up/down. Do you hear the small "click" of the relays? If not, the relay is stuck.
If the relay is welded, you cannot fix it in the field. The control board must be replaced. To prevent this, always use an "Interposing Relay" (a small 24V relay) when connecting the VFD fault output to high-current devices or inductive loads. Never connect the FL relay directly to a large magnetic contactor coil without a snubber/surge suppressor, as the kickback voltage destroys the relay contacts.
Description The "FL" terminals (FLA, FLB, FLC) are the main fault relay outputs of the drive. In some high-spec Toshiba drives (like G9/AS3), the drive monitors the status of this relay. If the CPU commands the relay to close, but the internal feedback detects it didn't close (or welded shut), it generates an FL system error. This ensures that if the drive faults, the external world (alarms/contactors) is reliably notified. Causes
1. Welded Contacts: The relay contacts have fused together because the user connected a high-current load (like a large solenoid) without a suppression diode.
2. Mechanical Failure: The relay mechanism is broken due to vibration or age.
3. External Voltage Backfeed: High voltage was accidentally applied to the FL terminals, damaging the monitoring circuit. Solution This is a hardware failure indication.
Listen to the drive during power up/down. Do you hear the small "click" of the relays? If not, the relay is stuck.
If the relay is welded, you cannot fix it in the field. The control board must be replaced. To prevent this, always use an "Interposing Relay" (a small 24V relay) when connecting the VFD fault output to high-current devices or inductive loads. Never connect the FL relay directly to a large magnetic contactor coil without a snubber/surge suppressor, as the kickback voltage destroys the relay contacts.
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