Rockwell Automation 20M LPM15 Liquid-Cooled Adjustable Frequency AC Drive FRN 2.xxx - Manual (Page 115)

Application Notes D-5
average rather than assumed values. For example, a 480V installation would
have a 480V AC line and produce a nominal 648V DC bus. If the drive were
to react to a fixed voltage for line loss detect, (i.e. 533V DC), then normal
operation would occur for nominal line installations. However, if a lower
nominal line voltage of 440V AC was used, then nominal DC bus voltage
would be only 594V DC. If the drive were to react to the fixed 533V level
(only –10%) for line loss detect, any anomaly might trigger a false line loss
detection. Line loss, therefore always uses the 6 minute average for DC bus
voltage and detects line loss based on a fixed percentage of that memory. In
the same example, the average would be 594V DC instead of 650V DC and
the fixed percentage, 27% for “Coast to Stop” and 18% for all others, would
allow identical operation regardless of line voltage.
The LPM15 can selectively use the same percentages or the user can set a
trigger point for line loss detect. The adjustable trigger level is set using
[Power Loss Level] (see
[Power Loss Level] on page 3-18 ).
Figure D.1 Power Loss Mode = Coast
Figure D.2 Power Loss Mode = Decel
Nominal
73%
Bus Voltage
Motor Speed
Output Enable
Power Loss
Nominal
82%
Bus Voltage
Motor Speed
Output Enable
Power Loss