Category: Hitec UPS System Configurations Part 2
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Hitec UPS - System Configurations Part 2

Fig 5: Parallel Configuration (Inside Out)
Cross-Link
In the parallel configuration, the DRUPS modules and critical load is
connected to one output busbar. Where two separate systems are required,
a “cross-link” system is ideal as the two clusters normally operate as
independent parallel systems but when any module is taken out of
service, the cross-link breaker will close. The control system maintains
synchronism between the two clusters at all times. Redundancy can
therefore be shared between the two clusters. The cross-link will not be
closed under fault conditions so as not to propagate the fault from one
cluster to the other.

Fig 6: Cross-link Configuration
Isolated Redundant
If the critical load to be supported is greater than the UPS capacity
that can be achieved by connecting units in parallel, say for fault
current reasons, then the Isolated Redundant configuration provides a
means of achieving an N+1 redundant system. Fig. 7 shows that normally
individual units supply their own critical loads. A dedicated additional
unit (the "redundant" unit) provides the N+1 redundancy. When a unit is
taken out of service, e.g. for maintenance, the critical load will be
transferred, without interruption, to the "redundant" unit via the
redundant busbar circuit.
Additionally, when all units are available the available power from the
"redundant" unit can be used to supply the non-critical load. When a
unit is not available, the non-critical load will be transferred back to
the utility supply.
Distributed Redundant:
While the Distributed Redundant configuration is still an N+1 design
it does not have a dedicated additional (redundant) unit. Instead, this
role is shared equally among all the units. In normal operation each
DR-UPS is part loaded so that when required it can take up part of
another unit's critical load.

Fig 7: Isolated Redundant Configuration
The overall critical load is divided into N groups on each module. A
three DR-UPS unit example is shown in Fig.8. Each DR-UPS unit is
connected to its N groups of critical load through the primary input of
automatic transfer switches (ATS). The secondary inputs to the ATSs are
shared equally among the other units. So, when a unit is taken out of
service, each group of critical load will be transferred, without
interruption, to its own "redundant" unit by the ATS.

Fig 8: Distribution Redundant Configuration
Hitec Power Protection has the experience to deliver all the above
configurations. Obviously, modifications to each concept are possible to
even better suit your typical requirements.
Information associated with: Hitec - Dual Output & Rotary Diesel UPS
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