Power Loss 2-107
Power Loss Some processes or applications cannot tolerate drive output interruptions
caused by momentary power outages. When AC input line power is
interrupted to the drive, user programming can determine the drive’s
reaction.
Terms
The following is a definition of terms. Some of these values are drive
parameters and some are not. The description of how these operate is
explained below
Table 2.T PF70 Bus Levels
Ter m Definition
Vbus The instantaneous DC bus voltage.
Vmem The average DC bus voltage. A measure of the “nominal” bus voltage determined by
heavily filtering bus voltage. Just after the pre-charge relay is closed during the initial
power-up bus pre-charge, bus memory is set equal to bus voltage. Thereafter it is
updated by ramping at a very slow rate toward Vbus. The filtered value ramps at 2.4VDC
per minute (for a 480VAC drive). An increase in Vmem is blocked during deceleration to
prevent a false high value due to the bus being pumped up by regeneration. Any change
to Vmem is blocked during inertia ride through.
Vslew The rate of change of Vmem in volts per minute.
Vrecover The threshold for recovery from power loss.
Vtrigger The threshold to detect power loss.
PowerFlex 700
The level is adjustable. The default is the value in the PF700 Bus Level table. If “Pwr Loss
Lvl” is selected as an input function AND energized, Vtrigger is set to Vmem minus
[Power Loss Level].
Vopen is normally 60VDC below Vtrigger (in a 480VAC drive). Both Vopen and Vtrigger
are limited to a minimum of Vmin. This is only a factor if [Power Loss Level] is set to a
large value.
PowerFlex 70 This is a fixed value.
WARNING:
When using a value of Parameter #186 [Power Loss Level] larger than default, the
customer must provide a minimum line impedance to limit inrush current when the power
line recovers. The input impedance should be equal or greater than the equivalent of a
5% transformer with a VA rating 5 times the drive’s input VA rating.
Vinertia The software regulation reference for Vbus during inertia ride through.
Vclose The threshold to close the pre-charge contactor.
Vopen The threshold to open the pre-charge contactor.
Vmin The minimum value of Vopen.
Voff The bus voltage below which the switching power supply falls out of regulation.
Class 200/240 VAC 400/480 VAC 600/690 VAC
Vslew 1.2 VDC 2.4 VDC 3.0 VDC
Vrecover Vmem – 30V Vmem – 60V Vmem – 75V
Vclose Vmem – 60V Vmem – 120V Vmem – 150V
Vtrigger1 Vmem – 60V Vmem – 120V Vmem – 150V
Vtrigger2 Vmem – 90V Vmem – 180V Vmem – 225V
Vopen Vmem – 90V Vmem – 180V Vmem – 225V
Vmin 204 VDC 407 VDC 509 VDC
Voff 3 ? 300 VDC ?
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