Lucien Miller developed a wiring chart to help in sizing wiring for models – it's nine pages long and is an excellent general wiring reference.
Lucien's comments below:
There are several columns that are on the chart that should be explained:
Wiring Table Example
In order for electrical engineers to have nice round numbers on the wire charts, instead of finding the cross sectional area of a wire by taking Pi x R x R, they came up with a unit called "Circular Mils". Since 1 mil = 0.001 inches, they decided to just take the diameter of the wire, in thousandths of an inch, and just square that number to get a value that was proportional to the area of the wire. For example, If you have a wire that measures 0.020" in diameter, that is 20 mils, and the area is 400 Circular Mils.
For UL specs in household wiring, they require 300 circular mils of wire per amp of current. That is the value in the last column of the chart.
For wiring in our models over short distanges, 75 Circular Mils per amp is enough for battery leads and motor wires. That is what the 75 CM/A column is for.
When winding stators, since the wire is in direct contact with the stator which serves as a heatsink, and because in most applications you have a fair amount of air blowing through the motor, you can get by with only 60 Circular Mils of wire per amp, and that is what the 60MC/A column is for.
I also have the resistance in both Ohms per foot and Ohms per meter for people that want to calculate line losses in their wires or power leads.
Wiring Table
Lucien Miller developed a wiring chart to help in sizing wiring for models – it's nine pages long and is an excellent general wiring reference.
Lucien's comments below:
There are several columns that are on the chart that should be explained:
In order for electrical engineers to have nice round numbers on the wire charts, instead of finding the cross sectional area of a wire by taking Pi x R x R, they came up with a unit called "Circular Mils". Since 1 mil = 0.001 inches, they decided to just take the diameter of the wire, in thousandths of an inch, and just square that number to get a value that was proportional to the area of the wire. For example, If you have a wire that measures 0.020" in diameter, that is 20 mils, and the area is 400 Circular Mils.
For UL specs in household wiring, they require 300 circular mils of wire per amp of current. That is the value in the last column of the chart.
For wiring in our models over short distanges, 75 Circular Mils per amp is enough for battery leads and motor wires. That is what the 75 CM/A column is for.
When winding stators, since the wire is in direct contact with the stator which serves as a heatsink, and because in most applications you have a fair amount of air blowing through the motor, you can get by with only 60 Circular Mils of wire per amp, and that is what the 60MC/A column is for.
I also have the resistance in both Ohms per foot and Ohms per meter for people that want to calculate line losses in their wires or power leads.
Lucien Miller
Wiring Table PDF DOWNLOAD