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3.10.2 Parallel control bus connection
In cases of parallel operation, the communication between the units takes place through the control
bus cables.
Each parallel unit is equipped with an additional board "P13 – RPA Board" where the connectors J52 (A)
and J62 (B) are located.
A short control cable provided with a ferrite ring core links the parallel board "P13 – RPA Board" with the
parallel bus socket on which must be connected the control bus cables JA and JB on PCB "P34 – Bus
Interface".
All the parallel units are connected to the same control bus.
This connection allows:
•
The microprocessors of each unit to communicate with each other.
•
The oscillators of each unit to be locked together.
•
The regulation loops to compare the output current of each unit in order to equally share the Load
current.
For increased reliability, this connection is made with redundant cables.
In this way, communication is maintained between units in case one of the control cables should fail or
be accidentally damaged or disconnected.
The standard length of the control bus cable between two parallel unit is 40 ft / 12 m.
Maximal overall length of bus connection, between the first and the last unit, should not be longer than
276 ft / 84 m.
Verify that control wiring is run in individual separate steel conduit.
NOTE !
Under no circumstance should the control bus cable connecting JA (1/2/3/4/5) and
JB (1/2/3/4/5) be connected or disconnected after the system has been powered On.
UPS 1
JP3
JP4
JA1
JA
JB
JB1
JP2
JP1
SGS_750_RPA-IM0048_01US
The shield of the control bus cable, connected on JA and JB must be connected to ground with the
appropriate cable clamps fitted on the parallel bus socket.
It is important to place the units in sequence of their assigned number.
A unit number from 1 to 6 is defined by the setting of parameters and displayed on the panel (P1 to P6).
This number is also marked inside and outside the packaging.
Modifications reserved
OPM_SGS_ISG_M75_M75_2US_V010.doc
UPS 2
JP3
JP4
JA1
JA2
JA
JB
JB2
JB1
JP2
JP1
JA1 + JB1
Fig. 3.10.2-1 RPA System - Control bus connection
UPS 3
JP3
JP4
JA2
JA3
JA
JB
JB3
JB2
JP2
JP1
JA2 + JB2
Installation Guide SG Series 750 UL S2 & SG Series 750 T12 UL S2
Next parallel
unit 4, 5, 6
JA3 + JB3
Page 40/49
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