92 Rockwell Automation Publication 20C-PM001F-EN-P - March 2012
Appendix B Application Notes
• [DC Bus Voltage] – displays the instantaneous value.
• [DC Bus Memory] – displays an estimate of the full-load DC bus voltage.
All drive reactions to power loss are based on either a fixed percentage of [DC
Bus Memory], a fixed DC bus voltage, or a user-programmable DC bus voltage.
The selected power loss mode determines which trigger levels are available, and
the choice of voltage levels is made by “toggling” a digital input programmed to
“Pwr Loss Lvl.”
If “Continue” is selected, the drive will ignore a loss of DC bus voltage and
continue to run the motor until the drive trips on an Undervoltage Fault (F004).
If “Decel” is selected, there is a choice of two levels for recognizing a power loss. If
a digital input is programmed for “Pwr Loss Lvl” but is not energized, or no input
is programmed, the drive will recognize a power loss at 80% of [DC Bus
Memory]. If a digital input is programmed for “Pwr Loss Lvl” and the input is
energized, a power loss will be recognized at the value of [Power Loss Volts].
If “Coast” is selected, there is a choice of two levels for recognizing a power loss. If
a digital input is programmed for “Pwr Loss Lvl” but is not energized, or no input
is programmed, the drive will recognize a power loss at 73% of [DC Bus
Memory]. If a digital input is programmed for “Power Loss Lvl” and the input is
energized, a power loss will be recognized at the value of [Power Loss Volts].
Figure 4 - Power Loss Mode = Coast
Figure 5 - Power Loss Mode = Decel
Nominal
73%
Bus Voltage
Motor Speed
Output Enable
Power Loss
Nominal
80%
Bus Voltage
Motor Speed
Output Enable
Power Loss
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