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Topic: Best Way to Connect for High Current Applications? (Read 1 time) previous topic - next topic

AlphaZeta

Hi guys,

I am currently working on an application that uses Arduino to control a Triac. The on-state current would be around 30A and I am a little concerned with the soldering joint (The Triac I am using is BTA41-800B which is soldered on to a circuit board).

Anyway, my questions are:

1. Would the solder joint be able to handle that (I assume that on the triac side has to be soldered since it's the standard TO-xx packaging)?

2. The wire I am using is 10 AWG, what is the best way to connect the load to the Triac? Should I use wiring nuts or will soldering do the trick? (I have no problem with soldering two 10 AWG wires, again I am just a bit unsure whether the joint would be able to handle the sustained high current).

Any suggestions are appreciated! Thanks.

br3ttb

I just finished a triac project of my own, and I'm not sure I did a great job in this area.  I'd also be interested in hearing what people have to say.

RuggedCircuits

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Would the solder joint be able to handle that (I assume that on the triac side has to be soldered since it's the standard TO-xx packaging)?


If the leads of the package can handle it then the solder joint certainly should.

I would lay down wide PCB traces and cover them with solder, all the way from the triac to the 10 AWG wire connector. That should handle 30A, though you may want to check the cross-sectional area of that solder blob against the cross-sectional area of 10AWG wire.

Finally, the conductivity of solder is not as good as that of copper. This chart shows percent conductivity (relative to annealed copper, known as IACS) of various solders....most have less than 10% the conductivity of copper:

http://www.microwaves101.com/encyclopedia/SolderChart.cfm

So....it's a tough question is what I'm saying :)  Put down big, wide tracks, cover with solder, then slowly start turning up the current and see how hot it gets. That's what I'd do....

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AlphaZeta

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If the leads of the package can handle it then the solder joint certainly should.


The leads look awfully thin for a maximum 40A load current the TRIAC can handle. But I am guessing this is because the leads are rather short?

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I would lay down wide PCB traces and cover them with solder, all the way from the triac to the 10 AWG wire connector. That should handle 30A


Yeah, that's what I've been thinking as well. I guess I will have to test how that handles the load...

If I were going for a more flexible option, I'd need some sort of connectors that could handle this kind of load though... any thoughts other than using wiring nuts?

RuggedCircuits

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If I were going for a more flexible option, I'd need some sort of connectors that could handle this kind of load though... any thoughts other than using wiring nuts?


How about a barrier terminal strip:

http://documents.tycoelectronics.com/commerce/DocumentDelivery/DDEController?Action=srchrtrv&DocNm=6-1437657-3&DocType=CD&DocLang=EN

These are rated for 30A and will accept wire from 10AWG and smaller.

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mcgyvr

I hope you have a heatsink for the triac in this plan...

P_Wood

I have used wide-traces combined with a piece of bare wire lying on the trace with loads of solder. My application involved 90VDC @ 10A+ (probably twice that under stall), though.

deSilva

Just a rule of thumb: The diameter of copper wires should be 1 square mm per 10 A. But there is no true proportionality.. 30A should have 6 square mm, not 3....

AlphaZeta

Yeah, mcgyvr.

I have a heat sink which has a thermal dissipation of 60W should be plenty for the Triac for the 30A load...

AlphaZeta

After doing some more research, I stopped by the Homedepot and grabbed a couple of copper grounding posts (Homedepot has lots of products for this kind of high-current applications. Although they are mainly meant for home builders, these connectors can easily be adapted to any circuit designs). I then soldered one side onto the circuit board and soldered short 10AWG wires along the traces (I made sure that the traces were as short as possible) and then screwed in the 10 AWG wires for load connection.

From my load tests I can say that this had worked out quite well.

jackrae

deSilva
There is true proportionality, it's just that guys who state urban rules don't bother using their little grey cells to calculate what's really required and those that follow do so because they know no better.

Your 10A/sqmm  ties in fairly well, though a little more conservatively, with the figure we used to use when winding transformers many decades ago.  At that time we based current capacity on 1000A/sqinch  for half-hard copper winding wire. At those sorts of loads there was no concern with heating of tightly wound coils so open air cooled wires should be more than happy.

jack

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