PREMIUM DSP 40-80 KVA PF0.9 3/3 - UPS www.visionups.com
40
IV. PARALLEL OPERATION
4.
1 Introduction
Two (or more) identical DSP0.9 series UPSs can be interconnected for parallel operation.
The main purposes for parallel use of DSP0.9 series UPSs are:
-Redundancy for Increased Reliability
-Power Increase
Although recent UPS designs are perfect and have high MTBF figures, a second (or more) UPS
can be used in parallel with the first one, for supplying the critical load in case of any possible failure of
the first UPS. In such an application the faulty UPS is isolated automatically from the parallel system
and the other UPS (or UPSs) continues to supply the critical load. Use of Redundant UPSs in parallel,
therefore, provides increased reliability for the critical load connected to the parallel system output.
If power demand increases in a certain UPS application exceeding the power rating of an already
installed stand-alone UPS, a second (or more) UPS of the same model and power rating can be
added in parallel to the existing UPS to increase the output power capacity.
Schematic diagram of parallel connection of two DSP0.9 series UPS units is shown in Figure 4.1
Figure 4.1
Parallel Connection of two UPSs
3 PHASE
MAINS I/P
3 PHASE
AC
Output
Rectifier /
Charger
Battery
(Dual Polarity)
Maintenance
Bypass
Switch
Static
Bypass
S2
(F4-F5-F6)
S1
(F1-F2-F3)
S5
(F10-F11-F12)
S3
S4
(F7-F8-F9)
Inverter
K2
K1
̃
-
-
̃
SB
Rectifier /
Charger
Battery
(Dual Polarity)
Maintenance
Bypass
Switch
Static
Bypass
S2
(F4-F5-F6)
S1
(F1-F2-F3)
S5
(F10-F11-F12)
S3
S4
(F7-F8-F9)
Inverter
K2
K1
̃
-
-
̃
SB
