Cabling, Auxiliary Equipment And Circuit Breakers - Rectifier RT9- 24V Installation, Operation And Technical Manual

Installation, Operation and Technical Manual Rectifier Technologies
conditions, the MOVs are expected to provide transient protection for the life of the
rectifiers.
If the transient environment is more severe, with a high incidence of lightning strikes either
indirect or direct, and/or severe switching transients beyond the levels outlined in the
standard, then supplementary transient protection is required. Larger MOVs (40kA rating)
are required at the AC main switchboard where the power to the rack originates.
For wiring systems where the neutral is bonded to the building earth at the main
switchboard (as used for example in Australia, USA, and Canada), one MOV from line-to-
neutral is required for single phase, and three MOVs from each line-to-neutral are required
for three phases.
For wiring systems where the protective earth is bonded to the neutral conductor only at
the distribution transformer, as is common in Europe, three MOVs are required for a single
phase (line-to-neutral, line-to-earth, neutral-to-earth), and seven MOVs are required for
three phase wiring (phase-to-neutral x 3, phase-to-earth x 3 and neutral-to-earth).

4.1.4 Cabling, Auxiliary Equipment and Circuit Breakers

In general, the system needs to have most of the following modules: AC Module, DC
Distribution Module, Battery Circuit Breakers, DC Cabling, Battery Current Transducers,
Temperature Sensors and AC Monitoring Module (optional).
These modules are required inside the rectifier rack for normal system operation. A brief
description of the modules and what they connect to is given below, along with a detailed
rack wiring diagram in Figure 4.1 that shows a system using a MUIB interface.
AC Module: An enclosure containing all the AC circuit breakers (curve C or D) for the
rectifiers, single or three phase active links, neutral links and main protective earth link for
connection to the installation AC system. In any system larger than 3kW, it is advisable to
balance the loads between all three phases. Consultation of local supply authority
requirements is advised.
Note that when using the RT9/10/11 units without a battery, the AC circuit breakers must be a curve-
D type (motor start). This is required to prevent false tripping of the circuit breaker when there are
half-cycle mains interruptions and the subsequent surges. Systems with a battery do not have this
requirement.
DC Distribution: An enclosure containing all the DC load distribution circuit breakers and
usually the Battery string circuit breakers. If the Battery breakers are included in the DC
distribution module, an isolation barrier is usually required along with clear labelling which
battery string the breakers are protecting. The input to the DC distribution module comes
directly from the DC output line of the rectifiers that is NOT connected to the system (DC)
earth.
DC Cabling: The choice of DC cabling and/or busbars is based entirely on the DC current
rating of the system. Consult the local National wiring standard for the selection of
cable/busbar size for the DC connections. One suggested method of DC cabling for
medium systems (~6-8kW) is to provide short 100mm x 6mm busbars at the external DC
interface with a number of holes to attach smaller DC cables. Then connect cables up to
2
25mm from the DC terminations to the output terminals of the individual magazines. The
flexibility of the DC cables can be a benefit over fixed busbars when fitting components
into a rack with limited space.
158-1872-01 9 19-Feb-14