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TW 3700 • TW 5550
Special case: Should the V
maximum amperes (Column 2). In this case, the correct wire gauge is selected
directly from the first two columns of the table.
Example: A 20 ampere (I
drop (V
) along its 15-foot cable (one way cable length) requires (by formula)
loss
a Column 3 resistance value of 0.083. This corresponds to wire gauge size 8
AWG.
If the cable length was 10 feet, the Column 3 value would be 0.125 and the
corresponding wire gauge would be 10 AWG.
3.
Aluminum wire is not recommended due to soft metal migration at the terminals
that may cause long term (on the order of years) poor connections and oxidation.
If used, increase the wire gauge by two sizes (e.g., specify 10 gauge aluminum
instead of 14 gauge aluminum).
4.
Derate the above wire gauge (use a heavier gauge) for higher environmental
temperatures since conductor resistance increases with temperature.
Temperature
ºC
ºF
40
104
5.
Derate the above wire gauge (use a heavier gauge) for an increased number of
current carrying conductors. This offsets the thermal rise of bundled conductors.
Number of
Conductors
3 to 6
Above 6
6.
The preferred insulation material is application dependent. Elgar's recommend-
ation is any flame retardant, heat resistant, moisture resistant thermoplastic
insulation rated to a nominal 75 C ( 167 F). Voltage breakdown must exceed the
combined effects of:
•
The rated output voltage;
•
Transient voltages induced onto the conductors from any source;
•
The differential voltage to other nearby conductors; and,
•
Safety margins to accommodate degradations due to age, mechanical
abrasion and insulation migration caused by bending and temperature.
Elgar TrueWave
requirement be very loose, I
loss
) circuit which may have a maximum 0.5 volt
peak
Current
Capability
80%
Current
Capability
80%
70%
Installation
may exceed the
peak
2-15
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