I noticed T200 uses AWG16 wires. Max current draw of T200 is 32A, which exceeds the 22A current rating of AWG16 wires. What’s the reasoning behind choosing 16A wires?
Thanks
The wire is very short. Remember Current is going to cause power drop over a length of wire run … and this could heat things up a whole lot. On the T200’s you have a short wire run and the thing is surrounded by a nice cooling medium.
You can get away with running a lot of current through a very short run with a lower gauge wire.
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I see. So power drop is what causes excessive heat? Does what material the coating of the cable is made from matter? I have seen a lot of different ratings for same size AWG wires. Some rated much lower than what an AWG table would tell you. And some rated much higher. Silicone wires tend to have a higher rating than pvc for instance.
Coatings … yeah they basically come into play during a rise in temperature. Silicone itself is a very good thermal insulator and will hold a wire that is getting hot a while longer. PTFE and Kynar are good too.
Just remember that “current” going through a “resistor” will dissipate energy. A wire has resistance based upon is cross section and the length of it. That is why I said a short piece can hang in there a lot longer than a piece with much greater length.
The type of conductor matters too. A lot of copper wire is just that copper. Then you start moving up to Tin, Nickel or Silver plated. Silver is your best conductor and most applications that require a lot of power use it for conductors or at least heavy silver plate on your electrical contacts.
To give you an idea, I designed one connector that the male pin was just engaging on tangent points for a contact about a half of an inch in diameter … we ran 750 amps through it for almost 6.5 hours to allow the temperature rise to get stable. The bus bar temperature only rose 20 degrees above room temperature after having that much current going through it for that long.
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Hi @uchiha,
This may be worth a read.
Electrical resistivity is basically a measure of how effectively electrical energy being transferred through a given medium/material is converted into other forms of energy. While that can include sound, light, and movement, in the case of wires that we use as conductors it’s mostly heat.
Applying an electrical potential (voltage) over a conductor induces a flow of charged particles, which is resisted to some degree by the conductor’s physical properties. Power drop isn’t so much the cause of heat generation as a measure of how much of the input power has been converted from electrical energy into something else (by the resistance).
Ratings are determined based on all properties remaining within desired/functional limits. Current ratings on wires are generally determined based on when the insulation would get excessively hot to the point that it can harm people, or cease to be effective (e.g. burn/melt off). Accordingly if you have very thick insulation, or just materials that are heat-resistant or very thermally conductive, the rating can be quite high. The properties of the conductor itself also matter, but generally our insulation materials get damaged well before the conductors do, and the electrical characteristics of a wire tend to stay mostly unchanged while in the usable temperature range (which isn’t the case for many components).
As @hscadden mentioned, the T200 wires are quite short and mostly surrounded by cool, and often flowing, water. Given that context, the temperatures that can be reasonably expected to occur are significantly lower than the “standard” testing conditions that most ratings are provided under.