Parallel Operation; Introduction - Tescom DS300SHPA Series User Manual

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1 Introduction

.
Two (or more) identical DS300SHPA series UPSs can be interconnected for parallel operation.
The main purposes for parallel use of DS300SHPA 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 DS300SHPA series UPS units is shown in Figure 4.1
3 PHASE
MAINS I/P
V. PARALLEL OPERATION
S3
Maintenance
Bypass
Switch
S2
(F4-F5-F6)
̃
-
K1
S1
(F1-F2-F3)
Rectifier /
Charger
(Dual Polarity)
S3
Maintenance
Bypass
S2
(F4-F5-F6)
̃
-
K1
S1
(F1-F2-F3)
Rectifier /
Charger
(Dual Polarity)
Figure 4.1 Parallel Connection of two UPSs
SB
Static
Bypass
-
̃ K2
Inverter
(F7-F8-F9)
S5
(F10-F11-F12)
Battery
SB
Static
Bypass
-
̃
K2
S4
Inverter
(F7-F8-F9)
S5
(F10-F11-F12)
Battery
47
S4
3 PHASE
AC
Output