Zhone IMACS 8000, Руководство пользователя

Страница: 49 / 788

Reference Guide 2-11
System Installation System Power and Ground Connections
2.6 System Power and Ground Connections
After installing the system power cards into the chassis, make the power and ground
connections to the chassis as described in this section. Each chassis has a terminal strip for the
DC voltage, ringing generator, and ground connections.
2.6.1 Chassis with Power Supplies
Figure 3-8 shows the terminal block on the chassis. Connections of external power to this
block controls which devices in the shelf will be powered.
For DC powered systems, the VA, and VB connections provide for separate, redundant power
feeds to the system's 8000-PS-DC power supplies installed in slots F1 and F2 respectively.
They are not used for systems with 8000-PS-AC power supplies equipped in slots F1 and F2
(AC powered systems). The VNA and VNB leads provide a connection for separate,
redundant power feeds to the system to provide "talk battery" or -48VDC loop feed to user
cards that require it. This includes talk battery for voice cards (FXS and FXO), signal battery
to E&M cards, and sealing current to OCUDP and ISDN cards. Also, the connection to VNA
powers the 8000-RG ringing generator if the generator is installed in the slot R1, and the
connection to VNB powers the 8000-RG ringing generator if the generator is installed in slot
R2. The VNA and VNB leads are not referenced to the VA and VB leads respectively. As a
result of this condition if you are running a DC system with -48VDC connected to the VA (F1
Power Supply) or VB (F2 Power Supply) leads only, you will not have any battery applied to
any of the user cards that require the -48VDC towards the CPE equipment. There must be a
separate 48VDC source applied to the VNA or VNB leads to provide the -48VDC source to
the connecting CPE equipment. If additional -48V feeds are not available for VNA and VNB
connections you may install a jumper from the VA or VB source leads using 16 gauge wires.
The VA or VB source feed must also be 16 gauge wires if a jumper between leads is required.
The telecommunications voice signaling ground is referenced ground connection to the
VNA+ side or VNB+ side of the -48VDC power system. Both of these feeds are referenced
to the same place on the backplane. This reference ground can occur at the Integrated Access
System power connection strip or at the -48VDC power source, which ever is more effective
if having multiple connections back to a ground source is not desirable. The wire connection
between the VNA+, VNB+, VA+, or the VB+ terminals, and a referenced ground is required
to eliminate ground isolation between connection devices. If this ground connection is not
maintained, and one side of the connection equipment is not referenced to an earth
ground then a floating ground condition can occur causing the voice circuits and the
voice signaling to react erratically when either end of the connecting equipment tries to
start the circuit.
When running the system in an AC environment with an AC/DC converter installed in the
chassis, the VNA+ or VNB+ must have the same ground reference as the connecting
equipment so as not to produce a floating ground potential as discussed earlier.