Rockwell Automation SP600 User Manual Version 3.0 - Manual (Page 143)

Parameter Descriptions 11-41
Sets the method and sequence of the DC bus regulator voltage
control. Choices are dynamic brake, frequency adjust, or both.
The user can select separate modes of control for Mode A and
Mode B through a configured logic input. When Both (3 or 4) is
selected, the bus controller will attempt to regulate the bus voltage
using the selected technique first and then swith to the secondary
method.
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. Test results have
shown that it takes between 2 and 12 seconds for a fault to
occur.