PUF means the DC BUS FUSE OPEN

The circuit detects that the DC Bus Fuse has opened

NEVER EVER RUN THE DRIVE AFTER REPLACING THE DC BUS FUSE WITHOUT CHECKING FOR SHORTED COMPONENTS (IGBT'S).

Common Causes
Shorted IGBT's (output transistors) or terminals

Corrective Action
Remove Power from the drive
Disconnect the motor
Perform checks across the IGBT
Set the DMM to diode check
Positive Lead on +DC Bus terminal and the Negative Lead on T1, T2, and T3. Readings should be low.
Negative Lead on +DC Bus terminal and the Positive Lead on T1, T2, and T3. Readings should be high.
Positive Lead on -DC Bus terminal and the Negative Lead on T1, T2 and T3. Readings should be low
Negative Lead on -DC Bus terminal and the Positive Lead on T1, T2 and T3. Readings should be high.
Replace the IGBT that has shorted as indicated by low, and low readings. Then replace the fuse.

When replacing the Insulated Gate Bipolar Transistors (IGBT), contact Milnor for guidance. They must be replaced as a set if there are two IGBT's in parrallel per positive or negative leg of the phase. It is generally good principle to also replace any filter capacitors, diodes that are in parrallel with the IGBT's as well. The short current from the IGBT which blew the fuse, may have caused damage to these components which could subsequently shorten their life.

CSH 01-14-09