Rockwell Automation Publication 520-UM001K-EN-E - August 2021 117
Chapter 3 Programming and Parameters
Advanced Program Group (continued)
A437 [DB Resistor Sel] Related Parameter(s): A438, A550
Stop drive before changing this parameter.
Enables/disables external dynamic braking and selects the level of resistor protection.
Options
0 “Disabled” (Default)
1“Norml RA Res” 5%
2 “NoProtection” 100%
3...99“3...99% DutyCycle”
IMPORTANT
When A437 [DB Resistor Sel] is set to a value greater than “0”, the value set in parameter A550 [Bus Reg Enable] will
not take effect.
A438 [DB Threshold] Related Parameter(s): A437
Sets the DC bus voltage threshold for Dynamic Brake operation. If DC bus voltage rises above this level, Dynamic Brake turns on. Lower values makes the dynamic braking
function more responsive but may result in nuisance Dynamic Brake activation (IGBT can modulate continuously).
Values
Default: 100.0%
Min/Max: 10.0/110.0%
Display: 0.1%
ATTENTION: Equipment damage may result if this parameter is set to a value that causes the dynamic braking resistor to
dissipate excessive power. Parameter settings less than 100% should be carefully evaluated to ensure that the Dynamic
Brake resistor's wattage rating is not exceeded. In general, values less than 90% are not needed. This parameter's setting
is especially important if parameter A437 [DB Resistor Sel] is set to 2 “NoProtection”.
A439 [S Curve %]
Enables a fixed shape S-Curve that is applied to the acceleration and deceleration ramps (including jog).
S-Curve Time = (Accel or Decel Time) x (S-Curve Setting in percentage)
Values
Default: 0%
Min/Max: 0/100%
Display: 1%
S-Curve Time
Total Time to Accelerate = Accel Time + S-Curve Time
50% S-Curve
Target
vel
Target
vel/2
S-Curve Time = Accel Time
Total Time to Accelerate = Accel Time + S-Curve Time
100% S-Curve
Target
vel
Example:
Accel Time = 10 s
S-Curve Setting = 30%
S-Curve Time = 10 x 0.3 = 3 s
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