Rockwell Automation Publication 20C-PM001F-EN-P - March 2012 9
Preface
ATTENTION: The sheet metal cover and mounting screws on the ASIC Board
located on the power structure are energized at (-) DC bus potential high
voltage. Risk of electrical shock, injury, or death exists if someone comes in
contact with the assembly.
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.
• 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).
• 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.
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