What can cause an Open Transistor Fault on the ATV66 Drives?

Issue:
ATV66 Open Transistor Fault

Product Line:
Altivar ATV66 and ATV56

Environment:
All

Cause:
ATV66 drive is tripping on Open transistor faults.

Resolution:
During power up the drive will perform an internal check of the IGBT's by switching on 2 transistors (from different phases) and then monitoring for current flow using the CT's.  If no motor is attached, this test is aborted.

The test will fail (and the Open Transistor Error will be triggered) if the current feedback measured by the drive is below the acceptable threshold). This testing is performed until all transistors have been tested.

Since IGBT's rarely will fail open, this fault normally indicates a connection issue between the drive and the motor or a problem in the motor itself (open winding, loose connection).  All motor wiring should be checked.   An ohm meter can be used to verify low resistance is measured between U, V and W on the drive (DRIVE MUST BE POWERED OFF, NO DC BUS VOLTAGE PRESENT).

If resistance is low and even between the phases, a static check of the IGBT's (inverter bridge) should be performed using a meter with diode scale as shown below:

If the IGBT's test OK , and the motor and wiring has been confirmed to be OK but the Open Transistor Fault remains: there are internal issues in the drive (likely Control board, gate driver board or current sensors).   Since the ATV66 drives have been discontinued since 2004, repair parts are no longer available and the drive should be replaced with a current product.

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