Power Loss
75
Power Loss Actions
The drive is designed to operate at a nominal input voltage. When voltage falls
below this nominal value by a significant amount, action can be taken to preserve
the bus energy and keep the drive logic alive as long as possible. The drive has three
methods of dealing with low bus voltages:
•
“Coast” - Disable the drive and allow the motor to coast.
•
“Decel” - Decelerate the motor at a rate which will regulate the DC bus until the
load’s kinetic energy can no longer power the drive.
•
“Continue” - Allow the drive to power the motor down to 50% of the nominal
DC bus voltage.
When power loss occurs, the “Power Loss” alarm bit in [Drive Alarm 1] turns on if
the respective bit in [Alarm Config 1] is enabled.
If the “Power Loss” bit in [Fault Config 1] is enabled, the drive will fault with a
F003-Power Loss Fault when the power loss event exceeds [Power Loss Time].
The drive faults with a F004-UnderVoltage fault if the bus voltage falls below V
min
and the UnderVoltage bit in [Fault Config 1] is set.
The pre-charge relay opens if the bus voltage drops below V
open
and closes if the
bus voltage rises above V
close
.
If the bus voltage rises above V
recover
for 20 ms, the drive determines the power
loss is over. The power loss alarm is cleared.
If the drive is in a “Run Permit” state, the reconnect algorithm is run to match the
speed of the motor. The drive then accelerates at the programmed rate to the set
speed.
Coast
This is the default mode of operation. The drive determines a power loss has
occurred if the bus voltage drops below V
trigger
. If the drive is running, the inverter
output is disabled and the motor coasts.
680V
620V
560V
500V
305V
407V
Bus Voltage
Motor Speed
Output Enable
Power Loss
Drive Fault
Pre-Charge
480V example shown, see
Table F
for further information.