GEH-6385 Reference and Troubleshooting, 2300 V Drives Chapter 3 Paramters/Functions
•
••
•
3-67
Diagnostic variables
The following table specifies the diagnostic variables of the Motor Ground
Protection function.
Variable Description
Gnd flt warning This variable is for external use to indicate that the alarm,
Ground flt alm, LP is present.
Gnd flt trip This variable is for external use to indicate that the fault, Gnd flt
trip is present.
Faults and alarms
The following table sp ecifies the faults and alarms of th e Motor Ground Protection
function.
Fault/Alarm Description
Ground flt al m, LP The alarm is present when Gnd cur signal >= Gnd signal alarm
on and is not presen t when when Gnd cur signal < Gnd signal
alarm off.
Gnd flt trip The trip fault occurs if Gnd cur signal >= Gnd signal trip lvl.
Function description
The VATF-MI D voltage feedback b oard provides a d irect measure of th e DC bus
neutral voltage to the control. This signal is filtered and conditioned to eliminate the
effects of bridge modulation and then mon itored.
With no motor ground fault condition, the voltage will be nearly zero. With a fault
to ground, the voltage will be at a maximum. For a partial ground fault condition,
which could be caused by damaged motor insulation, the voltage increases almost
linearly bet ween zero and the maximum voltage. The ground fault volt age, variable
Gnd cur signal is compared to thresholds to creat e the alarm or trip fault. Variable
Gnd cur signal is most sensitive at higher motor voltages. When a ground fault
condition exists, the alarm may be present at maximum motor voltage but may
disappear under oth er operating conditions.