Thanks for all the responses, it turned out to be solveable with sensorless vector speed control. The load was chaotically varying after running for a long time, as the contents of the drum got bunched up more and more into a cohesive mass. It rode up as the drum rotated, and slammed down when...
The times I personally witnessed it tripping was:
Once on acceleration, it tripped while the load was unevenly distributed inside the drum and started over-hauling the drive faster than the drive accelerated.
And once while it was running at a constant speed with a very light load. At the end...
We're struggling with a Beijer BFI P2 90kW VFD right now. 3 phase 400V. It's driving a large rotating drum for washing fishing nets. This means it's seeing a very varying load through a gearbox at roughly a 240:1 ratio. It's a tried and tested application, which to my knowledge has never...
