Another question about Sparx 3 phase wiring

I have just bought a Sparx 3 phase alternator and regulator rectifier. I am fitting it to my 1970 Roadster with its original positive earth system and Boyer ignition. Reading past posts it seems desirable to join up the black regulator rectifier wire direct to the battery (negative terminal) , but through its own fuse. The tests on the Tri-Cor site say that the alternator can generate up to 15.38 amps. I have some automotive wiring 15 amp wire which could be used between the fuse and the battery, - will that be sufficient or should I use some higher rated wire? What size fuse should I use?

Presumably I join the red wire from the regulator rectifier directly to an earth point on the frame; and ensure that the positive red wire that went direct from the battery to the old rectifier, which in turn was earthed, is now directly earthed to the frame?

All three yellow wires from the regulator to go to the three wires on the alternator.
Thanks for input.

Just for comparison, a 15 A circuit in a house requires #14 wire. That's probably a good place to start, but don't use solid, use stranded. If you can use larger, say #12, that would just mean less losses, but in all likeliness, you will not always be generating 15 A unless you're running full speed most of the time. Fuse, I would go with 17-20 A. Others with experience with the Sparx may have better info.

Dave
69S

DogT said:

Just for comparison, a 15 A circuit in a house requires #14 wire. That's probably a good place to start, but don't use solid, use stranded. If you can use larger, say #12, that would just mean less losses, but in all likeliness, you will not always be generating 15 A unless you're running full speed most of the time. Fuse, I would go with 17-20 A. Others with experience with the Sparx may have better info.

Dave
69S

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Speed has no bearing on the power generated, only the electrical load placed on the various circuits. 15A at 12 volts is 180 watts so unless you made your bike into a lighted dresser, you will only consume much less than 100 watts (headlight 55 watts, tail light 5 watts, brake light 21 watts, ignition 12 to 24 watt)

Jean

Jeandr said:

Speed has no bearing on the power generated,

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True, as usual I engaged my typing before I engaged the brain.

Dave
69S

Ran mine through the factory harness charging leads (brown/blue - red) behind the alternator but in front of the fuse. Also, ran a lead from one of the yellow wires out of the stator to the factory harness alternator lead (green/yellow) which signals the assimilator.

Since the wire on Nortons is stranded it will carry more amps than solid house wire. 16ga. stranded is rated for 20 amps, 14ga. is twice that, 40 amps. Reason being, conductors carry current on it's surface. A stranded wire has much more surface than a solid wire of the same diameter.

While AWG 16 is indeed rated for 20 Amps, AWG 14 has 60% more cross-sectional area, and is thus rated for 32 Amps, not 40. At frequencies below 7 kHz, for these wire sizes, skin effect is not active, and the current is carried uniformly across the entire wire bundle cross-section, solid or stranded. Stranded wire offers no electrical benefit even at high frequencies compared to solid wire except in the unusual case of individually insulated strands (Litz wire). Stranded wire is used in automotive applications (essentially DC) because of its mechanical flexibility.

While AWG 16 is indeed rated for 20 Amps, AWG 14 has 60% more cross-sectional area, and is thus rated for 32 Amps,

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I quoted the specs (ampacity) from this chart. http://www.rowand.net/Shop/Tech/WireCapacityChart.htm

Thanks for the correction.

Would the increase in surface area be 60% for stranded as well as solid when going from 16ga. to 14ga.?

Jim,

Stranded wire is most often quoted as "effective" AWG, which means that the copper cross-section of stranded 14 gauge, for example, is the same as a solid 14 gauge wire. The stranded 14 gauge wire will have a physical diameter 15% larger than the equivalent solid wire, which corresponds to the 33% difference in copper area of the two wires. Solid wire is more efficient dimensionally, stranded wire is more flexible.

Rick