2-72 Drive Overload
Figure 2.8 Normal Duty Boundary of Operation
The lower curve in Figure 2.9 shows the boundary of heavy duty operation.
In heavy duty, the drive is rated to produce 150% of rated current for 60
seconds, 200% of rated current for three seconds, and 220% of rated current
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 2.9 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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