User Manual Instruction Manual

Application Notes 13-87
13.34.2 Restart Power Restoration
If a power loss causes the drive to coast and power recovers the drive will return to
powering the motor if it is in a “run permit” state. The drive is in a “run permit” state if:
3 wire mode – it is not faulted and if all Enable and Not Stop inputs are energized.
2 wire mode – it is not faulted and if all Enable, Not Stop, and Run inputs are
energized.
13.34.3 Power Loss Actions
The drive is designed to operate at a nominal bus voltage. When Vbus 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 will have three methods of
dealing with low bus voltages:
• “Coast” – Disable the transistors and allow the motor to coast.
• “Decel” – Decelerate the motor at just the correct rate so that the energy absorbed
from the mechanical load balances the losses.
350 400 450
300
350
400
450
500
550
600
650
700
AC Input Volts
DC Bus Volts
Recover
Close
Trigger
Open
350 400 450
300
350
400
450
500
550
600
650
700
AC Input Volts
DC Bus Volts
Recover
Close
Trigger
Open
Line Loss Mode = Coast
Line Loss Mode = Decel
350 400 450
300
350
400
450
500
550
600
650
700
AC Input Volts
DC Bus Volts
Recover
Close
Trigger
Open
Line Loss Mode = Continue