Looking up the manual, I see 'Overtorque' detection. Modify parameters F615 to F619, pg132:
http://www2.schneider-electric.com/...=6DcU95ElLBxm4cOQjWl1eyMa3sr5DKLhtG4tk3a7jEQ,
That link doesn't work, but I have a feeling it's not going to an ATV12 manual. There is no "F615" in an ATV12.
Yes, this would have been a lot easier in something like a PowerFlex 520 series, but you don't have one of those. It does appear this drive is designed more as a "pump and fan" drive, so it doesn't have the kind of features typically found in machine control applications. So yes, it appears as though the closest thing you have available to you on that drive is the "Application Overload" function in I_O_; tOL and LOC. But you are correct, it is only adjustable down to 70% of the programmed motor FLC, plus it will only work if the motor is NOT accelerating or decelerating, meaning it has to be "at set speed", whatever that is. So if you are at 30-40 Hz, and assuming it's a 60Hz motor, you are at 50-80% speed, meaning it's most likely that your running current may ALREADY be lower than the lowest setting of that feature. That would mean you are not going to be able to use that.
The only other thing you can possibly do, as per DickDV's suggestion, is to program the Relay R1 (assuming you are not using it for anything else) as "I threshold reached" (Code CtA), then go to parameter Ctd (Motor current threshold) and set it to a value that corresponds to what you want to indicate. The "Motor current threshold" parameter can be set from 0-150% of the DRIVE'S current rating. So you will need to do a little math, and a little experimentation to find the right level. Then wire the NC side of that relay in series with the Run command (there is no External Trip function available for the Digital Inputs on that drive either, as he had suggested), then wire the NO side of the relay to a pilot light telling the operator what's going on.
If you are already using relay R1 for something else, you could use the triac output, L01. But that is essentially the equivalent of a "Normally Open" contact, but logically, you need it to be like a Normally Closed, to OPEN on the "Motor current threshold" trip. You can apparently change the logic using the next parameter for LO1, called LOis (I think) to nEG, meaning Negative Logic (I assume). The manual is typical for a Schneider manual, translated from French so it makes it difficult to understand.
{That's why I have always HATED Schneider drives as an integrator...}. That will not however leave you with any way to indicate why it has stopped. So it might mean running L01 to an external relay with a Form C contact and using like R1 above (in Positive Logic).
If you are using both R1 and LO1 for other important functions, I'm afraid you are SOL with that drive...