Drive Overload 2-87
Figure 2.18 Normal Duty Boundary of Operation
The lower curve in Figure 2.19 shows the boundary of heavy duty
operation. In heavy duty, the drive is rated to produce 150% of rated current
for 60 seconds, 200% for three seconds, and 220% for 100 milliseconds.
The maximum value for current limit is 200% so the limit of 220% for 100
milliseconds should never be crossed. If the load on the drive exceeds the
level of current as shown on the upper curve, current limit may fold back to
100% of the drive rating until the 10/90 or 5/95 duty cycle has been
achieved. For example, 60 seconds at 150% will be followed by 9 minutes
at 100%, and 3 seconds at 200% will be followed by 57 seconds at 100%.
With the threshold for where to take action slightly above the rated level the
drive will only fold back when drive ratings are exceeded.
Again, if fold back of current limit is not enabled in the [Drive OL Mode],
the drive will generate a fault when operation exceeds the rated levels. This
fault can not be disabled. If current limit fold back is enabled then a fault is
generated when current limit is reduced.
Figure 2.19 Heavy Duty Boundary of Operation
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0.90
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Current Level (Per Normal)
Time (Seconds)
Current Level (Per Normal)
Time (Seconds)
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