Manual 26174
EGCP-2 Engine Generator Control Package
Woodward
19
Shields and Grounding
An individual shield termination is provided at the terminal block for each of the
signals requiring shielding except for oil pressure and coolant temperature. All of
these inputs should be wired using shielded, twisted-pair wiring. The exposed
wire length, beyond the shield, should be limited to one inch. Relay outputs,
contact inputs, and power supply wiring do not normally require shielding, but
can be shielded if desired.
The EGCP-2 is designed for shield termination to earth ground at the EGCP-2. If
intervening terminal blocks are used in routing a signal, the shield should be
continued through the terminal block. If shield grounding is desired at the
terminal block, it should be ac coupled to earth. All other shield terminations
except at the EGCP-2 should be ac coupled to earth through a capacitor. A 1000
pF, 500 V capacitor is sufficient. The intent is to provide a low impedance path to
earth for the shield at frequencies of 150 kHz and up. Multiple direct connections
of a shield to earth risk high levels of current to flow within the shield (exception,
see note on cabinet installations).
Shields can be grounded at both ends (EGCP-2 and load) if the cable length is
sufficiently short (that is, within a cabinet) to prevent ground loop current in the
shield.
Cabinet Installations: If the EGCP-2 is installed in a cabinet, shielded I/O can be
terminated directly to the cabinet (earth ground) at the entry to the cabinet, as
well as at the EGCP-2.
For noise suppression reasons, it is recommend that all low-current wires be
separated from all high-current wires. Input Power ground terminal should also
be wired to earth ground.