Raymarine ALPHA, Руководство по установке, Страница: 44 / 72

Suitable for a vessel with a common RF ground point. In this scenario, the
power cable’s drain wire should be connected to the vessel’s common
ground point.
Battery connection scenario B:
Suitable for a vessel without a common grounding point. In this case, the
power cable’s drain wire should be connected directly to the battery’s
negative terminal.
Grounding
Ensure that you observe any additional grounding advice provided in the
product’s documentation.
More information
It is recommended that best practice is observed in all vessel electrical
installations, as detailed in the following standards:
• BMEA Code of Practice for Electrical and Electronic Installations in Boats
• NMEA 0400 Installation Standard
• ABYC E-11 AC & DC Electrical Systems on Boats
• ABYC A-31 Battery chargers and Inverters
• ABYC TE-4 Lightning Protection
10.5 Power cable extension (12 / 24 V systems)
If you need to extend the length of the power cable supplied with your
product, ensure you observe the following advice:
• The power cable for each unit in your system should be run as a separate,
single length of 2-wire cable from the unit to the vessel's battery or
distribution panel.
• Ensure that the extension cable is of a sufficient gauge for the supply
voltage and the total load of the device and the length of the cable run.
Refer to the following table for typical
minimum power cable wire gauges:
Cable length in meters
(feet) Wire gauge in AWG
(mm
2 ) for 12 V supply
Wire gauge in AWG
(mm
2 ) for 24 V supply
<8 (<25) 16 (1.31 mm
2
) 18 (0.82 mm
2
)
16 (50) 14 (2.08 mm 2 ) 18 (0.82 mm 2 )
Cable length in meters
(feet) Wire gauge in AWG
(mm
2
) for 12 V supply
Wire gauge in AWG
(mm
2
) for 24 V supply
24 (75) 14 (2.08 mm 2 ) 16 (1.31 mm 2 )
>32 (>100) 14 (2.08 mm 2 ) 16 (1.31 mm 2 )
Important:
Be aware that some products in your system (such as sonar modules)
can create voltage peaks at certain times, which may impact the voltage
available to other products during the peaks.
Important:
To ensure power cables (including any extension) are of a sufficient gauge,
ensure that there is a continuous
minimum voltage of 10.8 V dc at the end
of the cable where it enters the product’s power connector, even with a fully
flat battery at 11 V dc. (Do not assume that a flat battery is at 0 V dc. Due to
the discharge profile and internal chemistry of batteries, the current drops
much faster than the voltage. A “fully flat” battery still shows a positive
voltage, even if it doesn’t have enough current to power your device.)
10.6 Power cable drain wire connection
The power cable supplied with this product includes a dedicated drain wire
for connection to a vessel's Radio Frequency (RF) ground point (if available),
or the negative battery terminal.
The purpose of the drain wire is to drain excess voltage from the cable shield,
giving it a path to safety. The drain wire protects the cable's inner signal
conductors from electrical noise emitted by other cables and devices.
Although the drain wire is not intended to ground the product's internal
circuits, it's important that the drain wire is connected to the vessel’s common
RF ground point, which should be used for all equipment in your system.
If several items require grounding, the drain wires and dedicated ground
connections (if available) of all equipment should first be connected to a single
local point (e.g. within a distribution panel), and then this point connected via
an appropriately-rated conductor to the vessel's RF common ground point.
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