Coming into the final stages of a rebuild (replacing all turcite and some bearings) and retrofit of a cnc knee mill (5BVK, 4500 lbs) using machdrives servo drivers. I'm planning to use a chinese VFD (no speed control just on/off) rated for 7.5HP to drive the 5HP spindle motor and in the event that the VFD faults I want to avoid a crash. I was thinking of a either a relay powered by the logic control of the VFD or a NO reed switch on the power to the spindle motor in order to detect loss of power to the spindle and stop the servos. What would be the best way to implement this?
