IV404E Rev.000 SIEL S.p.A.
Issue date: 2017-06-05 Pag. 71 di 90 + FR
4.6
Operating modes
Several SAFEPOWER EVO HFT units connected in parallel share the current absorbed by the load between
them.
In a system with several UPSs connected in parallel, there is a single MASTER unit and the remaining units
will be SLAVES. The UPSs are all exactly the same and the MASTER is chosen on start-up. The MASTER unit
is shown on the
display panel by the capital letter “P” (or “B” in the case of a single battery). The MASTER
and SLAVE units may exchange roles. If a unit goes out of service, e.g. due to an inverter fault, it will
automatically be excluded. The load at this point is shared between the units that are still active; if the
power in output is excessive for the remaining UPSs, the system logic switches all the units, including the
UPS that was excluded, onto the by-pass line.
All the information contained in the section o
n “operating modes” (page
42 ) in relation to the UPS
remains valid with the addition of the information set out below.
ON LINE OPERATION
The message: “NORMAL OPERATION” is shown on the display panel of each UPS
and the letter “P”
appears in the bottom left-hand corner near the indication of the model. This letter is in upper case if the
equipment in question is the MASTER, while a lower case character is displayed if the UPS is a SLAVE.
STAND-BY ON OPERATION
The sharing of the load between the UPSs is linked to the length of the cables, and the rules on the length
of the connections indicated in the section “connections” must be observed. In the event of a mains power
failure, the load is passed onto all the parallel-connected UPSs.
STAND-BY OFF OPERATION
In this mode, if there is a mains power outage, the devices share the load equally; the load is not powered
with the mains present.
STABILIZER WITHOUT BATTERY OPERATION
In this mode, the devices share the load equally.
