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Open phase fault

The open phase fault stops the motor when one of the three motor phases appears to be disconnected or loose. The controller compares the currents in the three phases while running.

Prerequisites

Prerequisites

  • Motor setup is complete and the motor runs correctly.

How it works

When open phase fault detection is enabled, the controller compares the RMS currents of the three phases. If the difference between any two phases is greater than Open Phase Fault Detection Threshold for more than 1 second, the controller sets Open Phase Fault (Faults2 bit 14) and disables the motor phase bridge.

The fault clears with a fault clear command or a key cycle.

Configure the open phase fault

  1. Enable Level 1 Features bit 2 Open phase fault detection.
  2. Set Open Phase Fault Detection Threshold to the phase current difference, in amperes, that should trigger the fault.
  3. Save the parameters to flash.

To disable the open phase fault, disable Level 1 Features bit 2 Open phase fault detection.

Verify

  1. Run the motor through its normal load range.
  2. Check that Faults2 bit 14 does not set in normal operation. If it does, check the phase connections before you raise the threshold.

Troubleshooting

The fault triggers in normal operation

Check and fix the motor phase connections at the controller and the motor. One phase is likely disconnected or loose. If all connections are good, the threshold may be too low for your motor.

Parameters

Parameter Address Units Description
Level 1 Features 1880 Bit field. Bit 2: Open phase fault detection.
Open Phase Fault Detection Threshold 1966 A Phase RMS current difference that triggers the open phase fault.

Parameters used on this page