Connection Between Aluminum Bus Bar and Cooper Bus Bar

For the bolt connection I also recommend using a hardened washer with a Belleville washer on top of that. Steel, copper, and Aluminium all have different coefficients of expansion, and the softer metals tend to deform, so the hardened washer spreads the load over a larger area, and prevents the Belleville washer from simply deforming the copper or aluminium.

Once the connection is torqued, put a dab of paint on it to show you torqued it.

I don't recommend repeated re-torquing, because the softer metal will flow. The Belleville washer should maintain adequate tension.

Thermography of the joints will identify poor connections in the future.

I agree, definitely bad idea to ask a complete bunch of strange people for an electrical issue of this type.

Having noted that, Lyn gives good advice. Also good advice on proper tensioning the bolted joints and tinning the connections between dissimiliar metals.

Cooper? Are your bus bars made out of oaken barrel staves?

A good cooper could probably make some aluminum staves bus bars very easily. They already know how to make the steel rings.

Happy Holidays

Did you mean a Mini Cooper Bus?

.

.

....or did you mean one of the bigger ones.

.

Before proceeding...

You need to talk to the manufacturer and the certification organization that certified the switchgear (assuming of course that the gear is certified) to see what doing as you wish will do to the certification of the gear in question.

Of course... if you do not care about such issues... then have fun.

Assuming you mean Copper, not Cooper:

http://en.wikipedia.org/wiki/Aluminum_wire

Be sure to follow all electrical codes for your area.

phillip choi-

What ever you decide to do, if it is a mechanical connection you must use a copious quantity of anti-oxidant joint compound between the Al and Cu. This prevents further oxidation of the Al. At the juncture between the two the Al will form more oxidation which increases the resistance of the juncture which heats up the juncture which forms even more resistance and so on. Finally it gets to the point where it is so hot that the Al melts or adjacent plastic or combination plastic/metal components melt. At that point you have a sparking, flaming, exploding juncture. Not a happy experience.

Many brands are available. Ideal makes some called Noalox anti-oxidant joint compound.

I once had a bad connection in the house panel and the Al wire from the meter. Cu on main breaker was connected dry to the Al buss. Fortunately I discovered it before it got to the extreme heat stage. It was glowing and had small sparks though. Wouldn't whish that upon anyone.

Good Luck, Old Salt

htmlEditor - blank page
Galvanic Corrosion occurs between Joint of Aluminum and Cu. Resultant product increases contact resistance which results in heating.

When specifying any equipment with Aluminum Terminals or Bus bars, we specify that the bus bars/ Terminals shall be plated with Silver so that it is suitable for Connection to copper terminals or bus bars.

Additionally when making connection we smear surfaces in contact with rust inhibitor contact paste (available from Dowel's and others such as Jainsons in India).

General practice is, before making connections, to clean Al surface with emery paper to remove film of Aluminium oxide which has colour of dull Al and can not be differentiated. Note that this is only done on Al surface which is not electroplated with Silver - if you do this on coated surface, the coating will come out and make the contact worse.

If the Al surface at termination has not been protected with Ag coating, it is advised to use Bi-metallic washers of Cu-Al between the contact surface. You can easily find Al-Cu sintered together thin plates of approx. 1mm thickness. Procedure is:

1. Cut Bimetallic washers of same shape as contact surface.

2. Lightly clean Al surface at joint of bus bar and bimetallic washer with fine (120 grit or more) emery paper (use red colour paper. Black colour has Carbon in the binder and if sprayed on insulations can cause more problem). you will see brightness on rubbed surface.

3. Smear Rust Inhibiting paste on Al surfaces.

4. Make joints in such a way that Al of bus bar is in contact with Al of Bi-metalic washer and Cu bus bar is in contact with Cu surface of Bi-metalic washer.

5. Torque the bolts. Preferably use 8.8 Grade fastners for electrical joints.

best or luck

I suggest the best way to approach this is for you to develop a performance/environmental specification. Using this spec. will allow you to decide whether you require professional assistance, and if you decide you do, it will permit your consultants to help resolve your problems. We work with 300kA bus bars on a daily basis, but I wouldn't dream of providing you with our specification because it might not apply to your situation.