Newmar
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1580 Sunflower Ave, Suite 100, Costa Mesa, CA 92626
Technical Service: 800-241-3897
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E-mail: [email protected]
Illustration B: Surge Protection Types
A Type 2 surge arrester (SPD2) should be used in coordination with the incoming Type 1 surge arrester. This is the second
stage of protection. The Type 2 Surge arrester is designed to run-off energy caused by an overvoltage comparable to that of
an indirect lightning strike or an operating overvoltage (this is effectively the “left-over” surge from the Type 1 protection
device). To provide sufficient de-coupling between the Type 1 and Type 2 devices, impedance is required. This is typically
stated to be 10m of cable (approximately 10µH). This cable may be looped if the distance available is too short. Alternatively,
various manufacturers have devices which act as filter elements or provide active spark ignition for applications where 10m of
cable is not practical (such as outdoor enclosures).
Note: NewMar Rectifiers are compliant with EN61000-4-5, Level 4 without any external/upstream surge suppression. To
maintain a coordinated approach to surge suppression, Type 2 SPD should be installed upstream if not fitted in the system.
WARNING The fitment of a Type 2 AC Surge Suppression Device is mandatory.
If a Type 2 SPD
is NOT fitted, the warranty is void.
II.A
Upstream Over-Current Protection
There are three considerations to take into account when selecting an appropriate fuse/circuit breaker:
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Firstly, the upstream protection should protect the downstream cable from overload situations,
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Secondly, discrimination should be maintained with the downstream device fuses, and - Thirdly, protection of
the surge suppression devices should be taken into account.
II.B
Cable Rating
The maximum current drawn by this DC power system is 52.5A per phase (at minimum input voltage of 185V PhPh 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 in the protection device, making its minimum rating 63A. As a result,
typically 63A device is used. Therefore, the cable used to supply the system must be rated at the upstream protection device
rating. Please see your local wiring regulations for exact requirements, as cable sizes can vary depending on these regulations
and on the material the cable’s insulation is made from.
As a comment on rectifier AC feed cable sizes: each rectifier is fed by one set of cables from the AC input terminals.
Although in theory it may appear that this smaller wire is unprotected, in fact it is protected on two accounts. Firstly, it is
protected by the rectifier input fuse (which is only a short distance away). Secondly, the rectifiers are power-limited on their
input. Therefore, they can never be overloaded. As a result, the wire can never be over-loaded by the rectifier – it can only
see fault current.
