Rockwell Automation 20M LPM15 Liquid-Cooled Adjustable Frequency AC Drive FRN 2.xxx - Manual (Page 11)

Overview P-3
!
ATTENTION: Risk of injury or equipment damage exists.
DPI or SCANport host products must not be directly connected
together via 1202 cables. Unpredictable behavior can result if
two or more devices are connected in this manner.
!
ATTENTION: The “adjust freq” portion of the bus regulator
function is extremely useful for preventing nuisance overvoltage
faults resulting from aggressive decelerations, overhauling
loads, and eccentric loads. It forces the output frequency to be
greater than commanded frequency while the drive's bus voltage
is increasing towards levels that would otherwise cause a fault.
However, it can also cause either of the following two
conditions to occur.
1. Fast positive changes in input voltage (more than a 10%
increase within 6 minutes) can cause uncommanded positive
speed changes. However an “OverSpeed Limit” fault will
occur if the speed reaches [Max Speed] + [Overspeed Limit].
If this condition is unacceptable, action should be taken to 1)
limit supply voltages within the specification of the drive
and, 2) limit fast positive input voltage changes to less than
10%. Without taking such actions, if this operation is
unacceptable, the “adjust freq” portion of the bus regulator
function must be disabled (see parameters 161 and 162).
2. Actual deceleration times can be longer than commanded
deceleration times. However, a “Decel Inhibit” fault is
generated if the drive stops decelerating altogether. If this
condition is unacceptable, the “adjust freq” portion of the
bus regulator must be disabled (see parameters 161 and 162).
In addition, installing a properly sized dynamic brake
resistor will provide equal or better performance in most
cases.
Important: These faults are not instantaneous. Test results
have shown that they can take between 2-12
seconds to occur.