Datasheet

CSI SECTION 16611 STATIC UNINTERRUPTIBLE SYSTEM/PDU/DISTRIBUTION
CSI SECTION 16611 STATIC UNINTERRUPTIBLE SYSTEM
7
2.6 STATIC BYPASS
A. As part of the UPS, a system static bypass switch shall be provided. The system static
bypass shall provide no break transfer of the critical load from the Inverter output to the
static bypass input source during times where maintenance is required, or the inverter
can not support the critical bus. Such times may be due to prolonged or severe
overloads, or UPS failure. The UPS and static bypass switch shall constantly monitor
the auxiliary contacts of their respective circuit breakers, as well as the bypass source
voltage, and inhibit potentially unsuccessful transfers to static bypass from taking place.
B. The design of the static switch power path shall consist of Silicon Controlled Rectifiers
(SCR) with a continuous duty rating of 125% of the UPS output rating.
C. Automatic Transfers: An automatic transfer of load to static bypass shall take place
whenever the load on the critical bus exceeds the overload rating of the UPS. Automatic
transfers of the critical load from static bypass back to normal operation shall take place
when the overload condition is removed from the critical bus output of the system.
Automatic transfers of load to static bypass shall also take place if for any reason the
UPS cannot support the critical bus.
D. Manual Transfers: Manually initiated transfers to and from static bypass shall be
initiated through the UPS display interface.
E. Overloads: The static bypass shall be rated and capable of handling overloads equal to
or less than 125% of the rated system output continuously. For instantaneous overloads
caused by inrush current from magnetic devices, or short circuit conditions, the static
bypass shall be capable of sustaining overloads of 1000% of system capacity for
periods of up to 500 milliseconds.
F. Modularity: The static bypass switch shall be of a modular design.
J. System Protection:
As a requirement of UL1778, back-feed protection in the static bypass circuit shall also
be incorporated in the system design. To achieve back-feed protection, a mechanical
contactor in series with the bypass SCR(s) shall be controlled by the UPS/static switch,
to open immediately upon sensing a condition where back-feeding of the static switch
by any source connected to the critical output bus of the system is occurring. One such
condition could be a result of a shorted SCR.
2.7 DISPLAY AND CONTROLS
A. Control Logic: The UPS shall be controlled by two fully redundant, user-replaceable /
hot-swappable control modules. These modules shall have separate, optically isolated,
communication paths to the power and static switch modules. Logic power for the
control modules shall be derived from redundant power supplies, each having a
separate AC and DC input and output. The communication of the control modules
shall be of Controller Area Network (CAN Bus).