What is the minimum contact area to pass 1000 amperes with not more than 0.1 voltage drop between two coppers.

Question

1. I need to design a 1000 amperes output both on DC and AC 400 c/s. Output voltage is not more than 2 volts. I choose gauge 1/0 copper wire that is available in the company for engine generator. The biggest lug that I can get from my shop fit for 1/0 wire size. The lug marks 3/0 AWG letter on it. I guess it means the lug (the contact area) is only good to carry the current rate equivalent to AWG 3/0 wire. This lug is used to connect the aircraft engine generator with 1/0 brass wire.

The lug has tin clothing,the wire is not pure copper,it is copper compound. The wire has metal size of 1/0 but it marks down as a 2/0 AWG size of copper wire current rate. My design only need to run 500 till 1000 amperes not more than 120 seconds at a time. A 1000 amperes 2 volts transformer has a "U" sharp secondary in half circle made of copper. It has two big holes for the output to connect to lug. The contact area is 1.5"X3.5" ,thickness is 0.5". The hole is 1/2" dia. What is the lug area size?

Answer 1

For a 0.1V loss at 1000  Amps and 2 foot length (1 foot coming and going) of copper wire  the minimum size needed is 4/0 (drop = 0.101 V).  2 feet of 3/0 will give 0.127V drop.  You don't need to worry about heating because of the short cycle and short length of the wire.  A 1.5" by 3.5" contact area is about 5 square inches allowing for the hole.  That's almost 27 times the circular area of 4/0 wire (120 mm^2).  This should be more than sufficient.  Use large flat washers on both sides and torque the 1/2 inch bolt well to ensure a good connection.

Answer 2

The rule of thumb is 1sq-in of copper for 1000amps. This fact can vary based on insulation, heating affect/cooling affect of the devices, such as a fan or even an AC (air conditioner) in some cases to help cool the equipment.

The wire size doesn't make a difference regarding voltage, only the insulation rating. However, the insulation can affect the ampacity rating, see attached charts.

Your wire lug can be rated for 1/0 or 2/0, but the number of strands could cause you to go to a larger lug (ferrule) due to the Cross Sectional Area of the wire. If you have fine strands in the neighborhood of 285 for a 1/0 wire then possibly a 2/0 lug is required. The wire is still rated as a 1/0 for Ampacity. The way the wire is routed also affects the ampacity, such as in a raceway or open air.

You can double the wire ampacity by running wires in parallel. Having the lugs terminated back to back.

Since you are running for short periods of time, you could get by with a single cable. Ampacity is calculated due to heating affect. Most charts are figuring a continuous duty application.

Also, Amps are Amps when calculating wire size, doesn't matter AC or DC circuits.

The voltage drop across short runs of 1/0 wire and the large termination points should be no problem. Keep the runs under 3ft and you are good to go.