Ot Over-Torque Detection fault in Toshiba drive
Ot Over-Torque Detection fault in Toshiba drive
Description Ot is the opposite of UC. While OL (Overload) measures thermal heat accumulation over time, Ot is an instantaneous or short-delay torque limit trip. It acts as an electronic shear pin. It is used to protect machinery from physical damage when a jam occurs, often tripping faster than a thermal overload would. It signifies that the mechanical load has spiked unexpectedly, even if the current hasn't exceeded the absolute drive rating (OC). Causes
1. Mechanical Jam: A conveyor has a rock stuck in it, or a shredder has encountered an unshreddable object.
2. Brake Failure: The mechanical holding brake (on a hoist or elevator) failed to release, and the motor is trying to drag the locked brake.
3. Lubrication Failure: Bearings or gearboxes have seized up.
4. Acceleration settings: Trying to accelerate a heavy load too fast can trigger torque limits if the "Stall Prevention" is disabled. Solution Isolate the mechanical system immediately. Do not force the drive to run. Disconnect the motor from the load (remove belts or uncouple shaft) and rotate the driven load by hand. It should move relatively freely. If it is stuck, you have found your problem.
If the machine uses a mechanical brake, verify the brake timing. The VFD should send a signal to release the brake *before* ramping up torque. If the brake contactor is sluggish or the wiring is loose, the motor fights the brake, triggering Ot. Check the "Brake Release Frequency" parameter.
If the machine is old, friction may have increased. You may need to slightly increase the Over-Torque Detection Level (typically F616). However, be careful: increasing this reduces the protection for the machine. If you set it too high, the next jam might break a shaft or chain instead of tripping the drive. You can also adjust the detection time—allowing a 1 or 2-second spike (to push through a tough spot) before tripping.
Description Ot is the opposite of UC. While OL (Overload) measures thermal heat accumulation over time, Ot is an instantaneous or short-delay torque limit trip. It acts as an electronic shear pin. It is used to protect machinery from physical damage when a jam occurs, often tripping faster than a thermal overload would. It signifies that the mechanical load has spiked unexpectedly, even if the current hasn't exceeded the absolute drive rating (OC). Causes
1. Mechanical Jam: A conveyor has a rock stuck in it, or a shredder has encountered an unshreddable object.
2. Brake Failure: The mechanical holding brake (on a hoist or elevator) failed to release, and the motor is trying to drag the locked brake.
3. Lubrication Failure: Bearings or gearboxes have seized up.
4. Acceleration settings: Trying to accelerate a heavy load too fast can trigger torque limits if the "Stall Prevention" is disabled. Solution Isolate the mechanical system immediately. Do not force the drive to run. Disconnect the motor from the load (remove belts or uncouple shaft) and rotate the driven load by hand. It should move relatively freely. If it is stuck, you have found your problem.
If the machine uses a mechanical brake, verify the brake timing. The VFD should send a signal to release the brake *before* ramping up torque. If the brake contactor is sluggish or the wiring is loose, the motor fights the brake, triggering Ot. Check the "Brake Release Frequency" parameter.
If the machine is old, friction may have increased. You may need to slightly increase the Over-Torque Detection Level (typically F616). However, be careful: increasing this reduces the protection for the machine. If you set it too high, the next jam might break a shaft or chain instead of tripping the drive. You can also adjust the detection time—allowing a 1 or 2-second spike (to push through a tough spot) before tripping.
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