Rockwell Automation SP600 AC Drive User Manual Version 1.0 - Manual (Page 175)

Parameter Descriptions 12-45
Sets the method and sequence of the DC bus regulator voltage
control. The choices are dynamic brake, frequency adjust, or both.
You can select separate modes of control for Mode A and Mode B
through a configured logic input. When option 3 or 4 is selected, the
bus controller will attempt to regulate the bus voltage using the
selected technique first and then switch to the secondary method.
Mode B can be selected via terminal block assignment.
If a dynamic brake resistor is connected to the drive, Bus Reg Mode
A and Bus Reg Mode B must be set to option 2, 3, or 4.
161
162 Bus Reg Mode A
Bus Reg Mode B
Range: 0 = Disabled
1 = Adjust Freq
2 = Dynamic Brak
3 = Both - DB 1st
4 = Both - Frq 1st
Default: Mode A: 0 = Disabled
Mode B: 0 = Disabled
Access: 2 Path: Dynamic Control>Stop/Brake Modes
See also: 160, 163, 361-366
!
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.