power distribution blocks

not if it is connected directly to copper conductors!

in general , using AL cables can be done but be careful that the size of the cable will be bigger at the same current.

for example according to the load , you have descided to use 25mm2 cable , if your calculations depends on copper cables, this means that you have to use bigger size like 35mm2 or 50mm2 ( I'm not sure but you can ask help from cables suppliers or search the web for ready comparison tables)

regards

Yes, in the United States, if listed by UL (Underwriters laboratory) and listed by the manufacturer for this purpose.

Good Luck,

James

^{_{"Is the metal Aluminium is advisable for power distribution blocks in transition box for low voltage induction motors?"}}

In a word, No.

The main problem with mixing copper and aluminum in electrical circuits is in using aluminum conductors, not in using aluminum termination devices. Almost all mechanical compression lugs are aluminum and they can be used on copper or aluminum conductors without problems as long as they are listed or stamped with a mark that says "Cu/Al". Corrosion can sometimes be a minor issue, but they sell a lubricant call "No-Ox" which goes on the ends of the conductors before inserting them into the lug which prevents dangerous levels of oxidation due to electrolysis.

But if you use an aluminum conductor and terminate it on something that does not specifically state it is listed for use with Al, the the conductor can swell and contract with temperature, which makes the connection loose which increases the resistance, raises the temperature more and ultimately leads to failure.

Guest,

Power distribution blocks and terminal blocks are commonly made in copper or tin-plated aluminum. None are made or sold in bare (or non-plated) aluminum. Bare aluminum reacts very quickly with atmospheric oxygen to form a stable insulating layer of aluminum oxide on its surface. The tin plating layer on terminal blocks, wire lugs, and similar items prevents the creation of this oxide layer. Therefore, care must always be used to ensure that it is not removed.

However, wires made of aluminum are without any tin or other plating. Therefore you should assume that they are already coated with oxide. For this reason, a competent electrician will coat the end of an aluminum wire with an oxide inhibiting compound or paste and then wire brush it to cut through or remove this invisible oxide layer before terminating it.

Aluminum and copper have different coefficients of thermal expansion. Therefore as the wire and connector heat and cool, the tightness of the contact can change. Also, aluminum is a softer metal than copper, so it can deform more easily. Early aluminum wires were made with a fairly soft form of aluminum, but aluminum wires now made have a harder form; but it still deforms more readily than "soft" (annealed) copper.

Put these two characteristics of aluminum together and you have the potential for disasters. To prevent them from happening, you must remove the oxide before making the termination and you must have a termination which allows for differences in thermal expansion.

Back to your terminal block question: If you want to make the terminal block yourself, ensure that it is properly tin plated, and also ensure that any set screws are also tin plated. Also, put an oxide-inhibiting lubricant on the set screw threads so they won't "gall" or seize up. If you buy a terminal block, make sure that it is approved or listed for both aluminum and copper conductors and that its location is not subject to temperatures higher than it is listed or approved for. Finally, if this is for work in your own facility, I would suggest an annual inspection of all terminations, circuit breakers, fuses, and similar locations using an infra-red scanner or camera to detect the heating that comes before catastrophic failure.

--JMM

thanks jmueller,

a good explanation.really it is helpful

thanks again