Samlex America SDC-30 User Manual
DC-DC Step
Down Converter
Owner's
Manual
Please read this
manual before
operating your
converter
Model:
SDC-30
INSTRUCTION MANUAL
24 VDC TO 12VDC CONVERTER - MODEL NO. SDC-30 ITEM NO. 06174
SDC-30 is a 24 VDC (nominal) to 12 VDC (nominal) converter based on a high performance fixed frequency power switching regulator. It is
designed to deliver a maximum current of 30 A at an output voltage of 13.8 VDC
Features:
•
High efficiency switching regulator
•
Small size and light weight
•
Cycle by cycle current limiting
•
Over voltage , short circuit and reverse polarity protections
•
Temperature controlled fan for cooling
INSTALLATION AND OPERATION
General installation requirements
- Install the unit in a cool, dry, protected and well ventilated space
- The unit may be installed on top of a horizontal surface or on the bottom of a horizontal surface. The unit can be installed horizontally on a
vertical surface (fan should not be pointing up or down)
- The unit has a temperature controlled fan for cooling. The suction and discharge openings on the sides should not be blocked. The fan will
only come on if the unit gets hot.
Input and output connections
The unit has a terminal block with 4 male flat tabs (6.3 mm) for quick connection. One is for positive 24 VDC input (marked +24 V), two are
common negative for input and output (marked 0 V) and one is for positive 12 VDC output (marked +13.8 V).
CAUTION ! Please ensure that the polarity of the input connection is not reversed. Always connect the positive of the 24 V battery to
the positive terminal marked +24V and the negative terminal to any one of the two common negative terminals marked 0 V. A reverse
polarity connection will blow the fuse inside the unit
Sizing of input and output conductors. Conductors have resistance that opposes the current flow and produces voltage drop and heating. The
resistance is directly proportional to the length of the conductor and is inversely proportional to the thickness (area of cross-section). Thus, a
longer and thinner conductor will have higher resistance and will, therefore, produce higher voltage drop and more heating. The size of a conductor for a particular application will depend upon the maximum current it is required to carry and for what distance. The size of a conductor
is designated by AWG (American Wire Gauge) number. The smaller the AWG number, the thicker the conductor. The conductors should
be sized for a maximum voltage drop of 2%. The cables should be multi-stranded insulated copper cable rated for at least 90 º C and
preferably oil resistant. The cables can be bought at a welding / marine supply store.
Cables for 24 VDC input and 12 VDC output connections. The cables on the 24 VDC input side should be able to carry a maximum current
of approximately 25 A (for extreme conditions when delivering 35 A on the output at current limit at lowest 24 V input battery voltage of 20
V). To limit the voltage drop to 2%, use # 8 AWG for distance up to 6 ft. and # 6 AWG for up to 10 ft. The cables on the 12 VDC output side
should be able to carry the full 35 A current under current limit conditions. To limit the drop in voltage to 2%, use # 6 AWG multi stranded
cables to connect to the load for a distance of up to 6 ft. and # 4 AWG for a distance of up to 10 ft. Use female quick connect terminals (tab
size 6.3 mm) on the ends of the cables to enable connection to the male tabs of the terminal block
External fuses on the input and output sides: The input and output connections should be made through 32 V, 30A fast blow fuses (For
example “Bussmann” Type ATC-30 or ATM-30 automotive type fuses). The fuses should be connected in series with the positive input and
output cables. The fuse on the 24 V input side should be as close to the battery positive terminal as possible
overheating / melting of the input side cables in case of short circuit on the input side cabling (A battery can provide very large currents during
short circuit condition)
WARNING: The warranty will be voided if the above external fuses are not used
. This will prevent the possibility of
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