rell
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| posted on 1/10/03 at 04:38 PM |
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i did an experiment put some pvc cable in jery can with some petrol in this morning
it feels a bit tacky on the serface not good just put some in oil to see what it will do?
had a look in the maplin book there is only normal equipment cable. unlike rs which has cable specialy made for automotive industry. as put on my
previous post.
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Stu16v
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| posted on 1/10/03 at 07:08 PM |
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*backs arse in hedge slightly*
Yes, in retrospect my '300 amp' example is flawed, as it is assuming that both a 12 volt and 240 system will be driving a component of 0.8
ohm resistance, where as Rell correctly states the power (watts)is going to be totally different at the receiving end of the cable. But the point is
still the same, heavier duty cable is needed for lower voltage systems driving components that make the same power.
Cheers, Stu.
Dont just build it.....make it!
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Hasse
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| posted on 2/10/03 at 06:14 AM |
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Wire rating
A very short proposal:
Go for 1.5 mm2 wires for everything exept 10mm2 from starter to alternator and 16-25mm2 from starter to battery.
Use maximum 20A fuse to 1.5mm2 wire. This will in worst case cause a temperature rise of 30 degC in the wire ( on top of ambient temperature) just
before the fuse blows( about 25-28A).
Normaly PVC works fine with small amounts of everything chemical present in a car exept for brake fluid.
Avoid temperatures above +90 degC.
Regards
/Hasse
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rell
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| posted on 2/10/03 at 07:34 AM |
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sounds about right to me.
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mad4x4
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| posted on 7/10/03 at 12:57 PM |
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quote:
Originally posted by rell
yes stu this is right but it is a mater of power.
for example power (watts)= volts x amps
so for a 16watt fan current would be for 12 volt would be
amps = watts/volts
so
amps = 16w/12A
so
amps = 1.33A
lets try that with 240v
amps = watts / volts
so
amps = 16w/240v
so
amps = 0.067A
there for on 240v for the same power you would need a smaller cable
equipment wire is normaly 70 c pvc wire
when i say 70 c wire i meen 70 degrees c
tri rated is 85 c to 95 depending on who makes it
70 c is the temp the insulator can get up to befor it starts to brake down
Usuall y when working out power for an AC circuit (Mains) you would use
P=i*v* Cos a
where :
I is current
v is Voltage
a is the frequency in Hertz (eg 60).
When working out power in a DC circuit (Cars)
use
P = I * v * Cos a or P= I *v
In a DC circuit there is no frequency of alternating current so the phase part is set to 0 and due to Cos (0) being equal to 1 this simplifies to
P= I * V
Scot's do it better in Kilts.
MK INDY's Don't Self Centre Regardless of MK Setting !
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rell
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| posted on 13/10/03 at 06:53 PM |
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i think your geting confused with power factor on your ac
P = V X I X pf
the power factor is the angle the curent leads or lags the voltage depending on wether the load is inductive or capasitive on inductive loads the
curent lags and lead on capasitive.
the power factor is the cos of the angle that the curent lags or leads.
don't forget the voltage is mesured at rms values
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JoelP
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| posted on 13/10/03 at 08:35 PM |
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i was gonna mention RMS myself but didnt wanna argue with someone who knows more than me!
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