8
TRUNKGUARD
®
Fieldbus
Power Supply
TPS400
Grounding
The TPS400 carrier is provided with three independent
connection points relating to ground. This section
provides details of each connection point and provides
recommendations on connecting these grounds.
Case Ground
The CASE ground connection is for personnel
protection and should be connected to the local
structural ground in the panel or enclosure, typically
the incoming ac power ground, if available. The case
can also be grounded via the DIN rail.
Shield Ground
The SHIELD ground is the collection point for all of
the shields relating to the fi eldbus signals (both fi eld
and HOST-side). This may be directly connected to
ground, through a capacitor or via the HOST ground.
Note:
If capacitor is not used, only one SHIELD
ground is needed either at the power carrier
or at the HOST top end. However, if it is at the
power carrier, then connect SHIELD point to
GROUND.
Surge Ground
The SURGE ground is available for those installations
that use the SPM201 surge protection modules.
These are designed to divert very large/short duration
currents associated with surges (up to 20kA) and so
these should not be connected to the normal SHIELD
ground. When used for surge protection, the shorting
bar between these ground points must be removed.
Therefore, if no surge protection is being used, this
shorting bar must be always connected to ground.
Case Ground
Shorting Bar
Shield Ground
Surge Ground
Figure 5.
Grounding options
Recommended Ground Wiring
Practices
Moore Industries recommends the following ground
wiring practices:
• Any Moore Hawke product in a metal case or
housing should be grounded.
• The protective earth conductor must be
connected to a system safety earth ground
before making any other connections.
• All input signals to, and output signals from,
MooreHawke’s products should be wired using
a shielded, twisted pair technique. Shields
should be wired to the connector for the
specifi c trunk or spur and the SHIELD ground
connected as described above.
• The maximum length of unshielded input and
output signal wiring should be 2 inches.
Fieldbus cable shields are “carried through” the
TPS400 Carrier’s input/output terminals and require a
suitable, noise-free ground connection point.
If SPM201 Surge Protection Units are fi tted, their
securing screw must be installed per unit and the
TPS400 DIN Carrier must be connected to a low
impedance surge protection ground with a direct cable
of at least 10 AWG (10mm
2
cross-sectional area) from
the grounding lug provided.
