text: <s>[INST] PF525 driving a flywheel We have several flywheel-driven machines. About a year ago, we installed a 15HP Powerflex 525 drive in simple V/Hz mode with DB resistors on one of the machines. It's been running great for that whole time. We have it set up so the STOP input (terminal 1) is wired through the DB resistor thermostats, input 2 is Run FWD ,and input 3 is Run REV. Since it's replacing an across-the-line reversing starter that's in the midst of a bunch of hard-wired relay logic, Relay 1 is Ready/fault and will cause the relays that control inputs 2 and 3 to drop if the drive faults. This arrangement has been running fine on machine [/INST] Joe E. Try swapping the motors. If the second motor is low inertia (compared to the first motor), it might be more difficult for the VFD to regulate the motor speed. \\n </s>