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Earth
Stud
Fig.1.1 AC – DC Earth Link
4.2.1
UpstreamOver-currentProtection
There are two considerations to take into account when selecting an appropriate fuse/circuit
breaker.
The upstream protection should protect the downstream cable from overload situations.
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Discrimination should be maintained with the downstream device fuses.
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(i) Cable Rating
The maximum current drawn by the DC power system is 12.5A per 2kW rectifier (6.2A for 24V
system and 48 VDC/1 kW rectifier modules), or 37.3A (18.7A for 24V system and 48 VDC/1 kW
rectifier modules) per fully populated rectifier shelf at a minimum input voltage of 175V AC and
full output power. The upstream protection device must be able to supply this load under all
conditions without tripping. Therefore, typically at least 20% headroom is allowed for the
protection device, making its minimum rating 15A/per 2kW rectifier (7.5A) or 44.8A (22.5A) for
fully populated rectifier shelf.
Note: The current carrying capacity of cables is dependent on the type of cable used. Please
check with your local supplier and local regulations for appropriate sizing.
(ii) Discrimination
Discrimination ensures that the upstream circuit breaker or fuse does not blow if a rectifier input
fails (short circuit). Therefore it is important to ensure the upstream protection discriminates
with the internal fuse of the rectifier. The fuse used in the RM2048/24, C2R-2000, and C2RX-
2048 rectifiers is a slow-blow 15A fuse. The tripping curve for this is shown in Appendix 4 at the
rear of this manual.
A minimum circuit breaker to use for this system is a 20A, D-curve (note, a 20A C-curve breaker
will not discriminate with the rectifier fuse). Therefore, when used with the 2.5mm
supplied, a 20A, D-curve breaker should be used.
• Phone: 714-751-0488 • E-mail: techservice@newmarpower.com
AC-DC Earth Link
Isolated DC Output)
Newmar • PO Box 1306, Newport Beach, CA 92663
(Remove link for
5
2
cable
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