SECTION 8 |
Installation
35
cables rated at 105ºC / 77°F minimum. Do not use aluminum cable as it has higher
resistance per unit length. Cables 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 c
ause a disproportionate 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.
8.4.4 Fuse Protection In The Battery Circuit
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 cable will become red-hot, the insulation will melt and the cable will ultimately
break. This interruption 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 conditions, the fuse used in the battery circuit should
limit the current (should be “Current Limiting Type”), blow in a very short time
(should be Fast Blow Type) and at the same time, quench the arc in a safe manner.
This special purpose current limiting, very fast acting fuse will blow in less than
8 ms under short circuit conditions. Appropriate capacity of the above Class T fuse
or equivalent should be installed within 10 cm of the battery Plus (+) Terminal
(Please see table 8.2 for fuse sizing).
WARNING!
Use of an appropriately sized external fuse as described above is mandatory
to provide safety against fire hazard due to accidental short circuit in the
battery cables. Please note that the internal DC side fuses are designed
to protect ther internal components of the inverter against DC side
overloading. These fuses will NOT blow if there is a short circuit along the
length of wires connecting the battery and the inverter.
