User's Manual

User Instructions Section 5877
Spec. No. 582140000 (Models 802NLDB, 802NLEB and 802NL-B) Issue AQ, January 15, 2013
Chapter 3. System Operating Procedures Page 3-21
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MCA “POWER SHARE” FEATURE
Description
The MCA Power Share feature allows you to connect a Spec. No. 582140000 Power
System (referred to as “New Power System” in this document) to an existing DC power
system (referred to as “Existing Power System” in this document) instead of extending or
completely replacing the Existing Power System.
The MCA Power Share feature provides for the sharing of the total load in a controlled
manner.
When Power Share is programmed, the MCA in the New Power System adjusts Rectifier
output voltage per load demands to ensure proper sharing between the New and Existing
Power Systems.
Operating Modes
Depending on the systems’ configurations, their Rectifier capacities, their distribution load
capacities, and the Power Share configuration; four operating modes can occur.
Low Load Operation
When the total load current demand is lower than the programmed percentage value of
the total capacity of the New Power System that will initially feed the load (PS Initial
Capacity Limit), the New Power System voltage will be increased by the programmed
PS Voltage Offset forcing the New Power System to carry the load. Make sure that the
output voltage does not exceed the battery float range recommended by the
manufacturer. In this operating mode, no current will be delivered by the Existing Power
System.
Normal Load Operation
When the total load current demand reaches the PS Initial Capacity Limit, the New
Power System output voltage will be decreased by the PS Voltage Offset, allowing the
Existing Power System to deliver the remaining current up to the New Power System’s
maximum capacity. Both New and Existing Power Systems are now providing current to
the load.
High Load Operation
When the total load current demand exceeds the sum of the maximum capacity of the
Existing Power System and the PS Initial Capacity Limit of the New Power System, the
New Power System will deliver the remaining current up to the maximum of its capacity.
The two systems will then reach their maximum capacities. This operation may occur
when the batteries are being recharged, after a commercial AC failure for example.
Overload Operation
When the total load current demand is higher than the sum of the maximum capacity of
the Existing Power System and the maximum capacity of the New Power System, both
Existing and New Power Systems and the batteries will feed the load. The output voltage
will depend on the conditions of the batteries. This operation occurs if the total capacity
of the PCUs (rectifiers) is too low in relation to the need for increased current.
Requirements and Conditions
The two DC power systems must be connected in parallel as described in the Installation
Instructions (Section 5776).