GE GEH6505A - Manual (Page 11)

POWER LEADER™ Ethernet Gateway
Chapter 2 – Installation
7
manual) to record the devices attached to each
network and verify that each device on each
network has a unique address.
3. Modbus Concentrators may be used to add
POWER LEADER commnet devices to a
Modbus network. The Concentrator assigns a
Modbus-equivalent address to each commnet
device attached to it. See Section 2-7 for a
discussion of commnet and Modbus-equivalent
addresses.
NOTE: While Modbus Concentrators are counted
as regular Modbus devices, the commnet devices
attached to Modbus Concentrators do NOT count
toward the 31 device/network limit, but ARE
considered in the 247 address/network limit.
4. No connections between Modbus networks are
permitted, either directly or through repeaters.
5. Modbus networks are constrained to a
maximum 4,000 feet of communication cable
without repeaters.
6. RS485 repeaters may be used to extend the
wiring length of a Modbus network or to
provide isolation between runs of cable in a
Modbus network. Refer to GEH-6502 for
appropriate wiring lengths with repeaters.
2–7 Modbus Equivalent Addresses
A maximum of 31 Modbus devices can be
supported on a single RS485 network of the
Ethernet Gateway. However, the Modbus RTU
protocol permits up to 247 individual addresses to
be recognized. These additional 216 addresses may
be utilized by commnet devices attached to a special
Modbus device, the Modbus Concentrator.
Commnet is a communications protocol utilized by
many of the devices from GE’s POWER LEADER
family of power management devices. The Modbus
Concentrator is a Modbus RTU device that permits
commnet devices to be assigned Modbus-equivalent
addresses. Each Modbus Concentrator keeps track
of up to 32 commnet devices and directs traffic
between the Modbus network and the commnet
devices. To the Modbus network, the commnet
devices appear as valid Modbus addresses.
To provide seamless integration of commnet-
compatible devices into the Modbus RTU network,
the Concentrator directly maps commnet addresses
to equivalent Modbus addresses. The valid range of
commnet addresses recognized by the concentrator
is 300–514. These addresses are one-to-one mapped
to the equivalent Modbus address range of 33–247.
For a more detailed discussion of commnet devices
and the function of the Modbus Concentrator, see
GEH-6491, the Modbus Concentrator Users Guide.
Table 4 lists commnet devices supported by the
Modbus Concentrator (and the Ethernet Gateway).
Device Description
POWER LEADER EPM Full-function, three-phase electronic
meter with optional pulse initiation;
simple retrofit to existing
electromechanical installations. See
GEH–6302 for a full description.
POWER LEADER Meter Full-function three-phase meter with
optional protective relaying and
waveform capture. See GEH–5892.
POWER LEADER MDP
Overcurrent Relay Three-phase and ground protection
against overloads and rapid
detection of short circuits.
See GEK–100682.
Spectra ECM™ Advanced motor protection in full-
voltage-nonreversing (FVNR) and
full-voltage-reversing (FVR)
combination starter applications.
See GEH–6435.
MicroVersaTrip PM™ trip
unit in Spectra RMS™
molded-case circuit
breakers Overcurrent protection and optional
full-function metering and protective
relaying. See GEH–5934.
MicroVersaTrip PM™ trip
unit in AKR, Power
Break® and Power
Break® II insulated-case
circuit breakers. Overcurrent protection and optional
full-function metering and protective
relaying. See GEH–6273.
Table 4. POWER LEADER commnet devices supported by the
Modbus Concentrator.