What can cause an ATV66 to trip on Output Phase Fault intermittently?
1. Under some conditions, there maybe a possibility that motor currents may oscillate between motoring and regenerating, crossing the fault threshold multiple times. In some of these situations, increasing the damping setting may produce favorable results. If the drive is operating in the CT mode, reducing the IR compensation setting may reduce current oscillations. 2. Under lightly loaded conditions, increasing either the voltage boost or profile settings will increase motor current draw. This may require switching from VT NOLD to Normal operation. 3. If possible, verify what the motor magnetizing current is. This can be done either by reading it from the nameplate (if available) or by measuring the current when the motor is running unloaded. On some types of motors, this value is fairly low. This low value, couple with some current oscillations is enough to cause nuisance faults. 4. If a defect in the drive controller is suspected, take an actual output current measurement of each of the three motor legs with a True RMS meter. The measured currents should not vary from the average by more than 5% nor differ from the keypad by more than 5%. a. If measured currents vary from the keypad by more than 5%, verify all connections from the motor current sensors to the power board to the control basket. If the variance persists, replace the parts in the following order: flex cables, motor current sensors, power board, control basket. b. If the motor currents are unbalanced, measure output voltages for an imbalance of greater than 3% of the average. 5. The output phase common to two low readings may be due to a hardware problem. Run the transistor test in the autodiagnostic. Compare that result with the results of the inverter bridge test found on page 75 of the VD0C06S701 manual. Check connections between the control basket to the power board and, if applicable, to the gate driver board. If applicable, check connections between the power board to the gate driver board and from the gate driver board to the IGBT modules. If all of these connects are correct and the voltage imbalance persists, replace parts in the following order: flex cables, gate driver board, power board, IGBT module or control basket. 6. If output voltages are balanced, investigate cause of current imbalance. If possible, run motor across the line and measure for current imbalance. Verify all motor connections. Replace motor. 7. In multiple motor applications, use a separate motor overload and disable output phase loss detection. 8. Output phase fault protection can be disabled in situations where low current is normal or when using an output contactor. If this is to be disabled, make sure that wiring is OK and that adequate motor phase loss protection is provided by other means.