Emerson FM-3 - Manual (Page 245)

231
Diagnostics and Troubleshooting
FM-3 Specific Fault Descriptions
Figure 95: FM-3 display is used to display drive and FM-3 faults
Enc St
Certain encoder states and state transitions are invalid and will cause the drive to report an
encoder state fault. This is usually the result of noisy encoder feedback caused by poor
shielding or a faulty cable.
Enc HW
If any pair of encoder lines are in the same state, an encoder line fault is generated. The most
likely cause is a missing or bad encoder connection.
Pwr Mod
This fault is generated when a power stage over-temperature, over-current or loss of power
stage logic supply occurs. This can be the result of a motor short to ground, a short in the
motor windings, a motor cable short or the failure of a switching transistor.
Low Bus
This fault will occur whenever the voltage on the DC bus drops below 96 volts. The most
likely cause of this fault is a reduction (or loss) of AC power. A 50 ms debounce time is used
with this fault to avoid faults caused by intermittent power disruption.
Hi Bus
This fault will occur whenever the voltage on the DC bus exceeds 440 VDC. The most likely
cause of this fault would be an open shunt fuse, a high AC line condition or an application
that requires an external shunt (that is, a large load with rapid deceleration).