SamplexPower PST-300-12 Manuel Du Propriétaire page 31

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up to AWG #1. Wires thicker than AWG #1 are designated AWG 1/0, AWG 2/0, AWG 3/0
and so on. In this case, increasing AWG # denotes thicker wire.
The DC input circuit is required to handle very large DC currents and hence, the size of
the wires and connectors should be selected to ensure minimum voltage drop between
the battery and the inverter. Thinner wires and loose connections will result in poor
inverter performance and will produce abnormal heating leading to risk of insulation
melt down and fire. Normally, the thickness of the wire should be such that the voltage
drop due to the current & the resistance of the length of the wire should be less than
2%. Use oil resistant, multi- stranded copper wire wires rated at 90ºC minimum. Do not
use aluminum wire as it has higher resistance per unit length. Wires can be bought at a
marine / welding supply store.
effects of low voltage on common electrical loads are given below:
- Lighting circuits - incandescent and Quartz Halogen: A 5% voltage drop causes an
approximate 10% loss in light output. This is because the bulb not only receives less
power, but the cooler filament drops from white-hot towards red-hot, emitting much
less visible light.
- Lighting circuits - Fluorescent: Voltage drop causes a nearly proportional drop in
light output.
- Ac induction motors: These are commonly found in power tools, appliances, well
pumps etc. They exhibit very high surge demands when starting. Significant voltage
drop in these circuits may cause failure to start and possible motor damage.
- PV battery charging circuits: These are critical because voltage drop can cause a dis-
proportionate loss of charge current to charge a battery. A voltage drop greater than
5% can reduce charge current to the battery by a much greater percentage.
Fuse Protection in Battery circuits
A battery is an unlimited source of current. Under short circuit conditions, a battery can
supply thousands of Amperes of current. If there is a short circuit along the length of
the cables that connects the battery to the inverter, thousands of Amperes of current
can flow from the battery to the point of shorting and that section of the wire will be-
come red-hot, the insulation will melt and the cable will ultimately break. This interrup-
tion of very high current will generate a hazardous, high temperature, high-energy arc
with accompanying high-pressure wave that may cause fire, damage nearby objects and
cause injury. To prevent occurrence of hazardous conditions under short circuit condi-
tions, an appropriate fuse should be used in the battery circuit that will limit the current,
blow in a very short time and quench the arc in a safe manner. for this purpose, UL Class
T fuse or equivalent with Ampere Interrupting Capacity (AIC) of at least 10,000A should
be used (As per UL Standard 248-15). This special purpose current limiting, very fast act-
ing fuse will blow in less than 8 ms under short circuit conditions. Appropriate capacity
of the above Class T fuse should be installed within 7" of the battery Plus (+) Terminal.
The fuse will require a corresponding fuse holder.
Installation
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