Third wire infrastructure requirements:
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You must have a working voltage rating of 370 VDC minimum. |
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The third-wire cable should pass testing for complete isolation from the coax shield to the vessel ground at 500 V. |
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The loop resistance, for the entire link from topside to the Trawl Unit, must be less than 100 ohms. |
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You must ensure electromagnetic compatibility of the FX80 installation with respect to cables that are part of other systems used on board. |
There are three major components to the third-wire infrastructure.
Third-wire trawl cable
The third-wire trawl cable connects the Trawl Unit to the ship. The third-wire trawl cable you use should minimize power loss and signal attenuation. The 11-mm CB6000 armoured coax cable is widely used in the industry, satisfies the power and attenuation requirements, and
is recommended for the FX80 system. Other cable types with similar specifications to the CB6000 may be suitable, provided they include galvanized steel wire armour. Plastic-insulated steel-core wire and 8-mm armoured wire is unsuitable.
Third-wire deck cable
The third-wire deck cable connects the topside system units. Proper deck cable construction and layout, based on best practices for minimizing electromagnetic interference, are required
to attain a fast and reliable telemetry link over the third wire. We recommend using a high-quality telemetry cable, such as the RG214 coaxial cable or an impedance-controlled shielded twisted-pair
cable. You may also use excess third-wire cable. The chosen cable should be similar to those of antennas with carrier frequencies up to around 1 MHz.
Important
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Do not put switches or junctions in the cable. |
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Do not use screw terminals. |
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Each connection should be crimped or soldered with all conductors intact. |
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Do not run the cable by factory equipment or with power cables. |
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Run in a conduit if at all possible. |
Third-wire slip ring
The third-wire slip ring connects the trawl cable and deck cable at the winch. The slip ring is a critical system component for both power and telemetry. A quality slip ring provides continuous, steady contact during the winch operation. The slip ring and the associated wiring must be enclosed in a metal housing with a good electrical connection between the
housing and the winch frame.
TipUsing slip rings with waterproof connectors, such as the Focal model 180, allows for easy testing and service.