Rockwell Automation 20G PowerFlex 750-Series AC Drives - Manual (Page 159)

Rockwell Automation Publication 750-RM002B-EN-P - September 2013 159
Diagnostics and Protection Chapter 3
Inverse Time Protection
The following curves show an example of the boundary operations of a
20G1AxC770 drive. The curve is defined by the drive’s continuous rating and the
respective overload capacities. These are voltage class and duty rating dependant
and are configurable by P305 [Voltage Class] and P306 [Duty Rating]. This
particular example has six different overload ratings.
• Low Voltage/Normal Duty or High Voltage/Normal Duty
• Low Voltage/Heavy Duty or High Voltage/Heavy Duty
• Low Voltage/Light Duty or High Voltage/Light Duty
Light Duty is only available to frame 8 and larger drives.
If the load on the drive exceeds the level of current as shown on one of the curves,
the inverse time protection increments the overload counter. Current limit can
fold back to 100% of the drive rating when the drive over load count reaches
97.35% until the 10/90 or 5/95 duty cycle has been achieved. For example, 60
seconds at 110% is followed by 9 minutes at 100%, and 3 seconds at 150% is
followed by 57 seconds at 100%. With the threshold for where to take action
slightly above the rated level the drive only folds back when drive ratings are
exceeded. If fold back of current limit is not enabled in P940 [Drive OL Mode],
an F64 “Drive Overload” fault occurs when operation exceeds the rated levels.
Normal Duty / Low Voltage
Normal Duty / High Voltage
Heavy Duty / Low Voltage
Heavy Duty / High Voltage
Light Duty / Low Voltage
Light Duty / High Voltage
Drive Overload Curve
Time to Trip (Seconds)
Cu
rr
en
t (A
m
ps
)