Rockwell Automation 1608M MegaDySC User Manual, 208 Volt, One Second Extended Runt - Manual (Page 21)

Rockwell Automation Publication 1608M-UM003A-EN-P - April 2014 21
Chapter
5
Operation
System Description Raw utility power enters and routes through the Automatic Bypass switchboard
to the load. In maintenance bypass mode the power bypasses the MegaDySC
cabinet and passes directly to the load. In this mode the load is unprotected from
voltage sags. In the Normal operation mode the MegaDySC cabinet is energized
and the power is directed through the MegaDySC, protecting the load. See the
following sections for MegaDySC and Automatic Bypass operation details.
MegaDySC Operation The MegaDySC section contains three power electronics modules (one module
per phase) and controls that continuously monitor the line voltage. The modules
are series-connected to the input line, and operate by adding the compensating
voltage needed to restore the line to its nominal output. When the utility line
voltage is within normal range the ac static switch components remain closed and
no compensating voltage is added. When an insufficient line voltage event
occurs, the static switches open and the sag-correcting electronics quickly add the
balance of voltage necessary to regulate the load voltage.
The MegaDySC accepts line input power over 3 wires into terminals R
in
, S
in
, T
in
and provides sag compensated three-phase output power at terminals R
out
, S
out
,
and T
out
when not in the Maintenance Bypass mode. In 4-wire systems the input
Neutral is connected directly to the output Neutral terminal.
Thermal switches are included to activate fans if the cabinet temperature or other
internal temperatures exceed set limits.
A touchscreen display provides indication of the status of the MegaDySC
operation. After power is switched on, the green “OK” box will be displayed in
the upper left hand corner of the display, indicating that the output voltage is
within a normal range of -13% to +10% of nominal.
A red “FAULT” box is displayed in the upper left hand corner of the display
when a fault condition is present on the MegaDySC. During this period sag
correction is disabled and the MegaDySC will continue to bypass the utility
voltage directly to the load through the static bypass path.
An orange “FAULT OVER” box is displayed when the previous fault condition
has cleared. Sag correction will remain inhibited until the reset period expired
(approximately 1 minute). A blue “SYSTEM OFFLINE” box is displayed
IMPORTANT Operation in Normal Mode requires that the maintenance bypass circuit
breaker (CBB) be open (OFF)—otherwise CBB will short the sag correction
inverter and prevent sag correction.