Rockwell Automation Liqui-Flo DBT Reach Drive - Manual (Page 69)

Parameter Descriptions 3-43
Selects whether the internal or an external DB resistor will be used.
If a dynamic braking resistor is connected to the drive, Bus Reg Mode A and B (161
and 162) must be set to option 2, 3 or 4.
!
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.
Note that these faults are not instantaneous and have shown test results
that take between 2 and 12 seconds to occur.
163 DB Resistor Type
Range: 0 = Internal Res
1 = External Res
2 = None
Default: 2 = None
Access: 1 Path: Dynamic Control>Stop/Brake Modes
See also: 161, 162
!
ATTENTION: Equipment damage may result if a drive mounted (internal)
resistor is installed and this parameter is set to “External Res” or “None.”
Thermal protection for the internal resistor will be disabled, resulting in
possible device damage. Failure to observe this precaution could result
in equipment damage.