Help with track width

[yoannes]

Hi,

I need help to dimension the size of a track. I am making an circuit with BTA26 and I need to make a track that can resist 380V 40A
Can someone help?

 

[sivamani]

refer

**broken link removed**

 

[andre_luis]

Yoannes,


If you use this graph bellow as guideline, results a value from about 400 mils, that is impracticable.
So, a mask solder coverage must be applyed over track in order to allow reduce width.

TRACE CURRENT CAPACITY

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[FvM]

0.4" (10 mm) trace/copper pour width isn't necessarily impracticable. I'm not aware of solder coverage considered as a reliable way to increase current capacity (e.g. in standards). Please correct me, if I'm wrong in this point. By the about factor 10 higher resistivity, solder must be quite thick to achieve a considerable effect.

For compact PCB layout, higher copper weight or paralleling layers should be considered.

 

[andre_luis]

0.4" (10 mm) trace/copper pour width isn't necessarily impracticable...

FvM,


Once TO220 is encapsulated in a BTA26 package, pinout spacing is 2,54mm, resulting distance inter tracks less than is required, wright ?


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[FvM]

BTA26 has TO3P package with 5.5 mm pin distance, this doesn't basically change the problem. It will help you at least to provide the required clearance without conformal coating or milled PCB slots.

Imagine the track end segment as a triangle with a corner at the pin rather than a round pin of full track width.

If you have wide tracks or copper pours on a power PCB, the thermal calculation will end up in determining point-to-point resistances, acceptable voltage drops and overall power dissipation. The risk of local overheating must be still kept in mind, but considering the lateral thermal conductivity of the copper structures.

An additional comment on the said solder coverage. I know that it's used in some circuits, e.g. SMPS. In my understanding, it will be utilized to reduce the track overtemperature and total power dissipation below permitted maximum values. But it's no reliable method if the copper structures don't have sufficient current capacity, e.g. because you can't guarantee a certain solder layer thickness.

BTA26 rated current is 25A, not 40A by the way.

 

[andre_luis]

...Imagine the track end segment as a triangle with a corner at the pin rather than a round pin of full track width...

I agree with you that punctual overheating at thin track can be dissipated over the larger track body.
I already proceeded this approach in a circumstance when solder mask cost must be avoided, but if possible I myself prefer this option.

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[yoannes]

Thank-you for the answers.

I made mistake, my circuit is 220V 15A max, so I will use an BTA26 for ensurance.

I'm thinking to use 2 OZ copper board with track width of 86 mils, accourding to the calculator it works fine.

 

[Elk Ebert]

15 amp continuous will require a track with of 0.14", download the PCTEMP calculator UltraCad Design, a very useful tool! E

 

[andre_luis]

...I'm thinking to use 2 OZ copper board with track width of 86 mils, accourding to the calculator it works fine.

Depending on PCB size, or if have mainly more logic than power circuitry, could be cheaper to place a solder coverage than specify 2OZ thickness against 1OZ.


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[yoannes]

I believe its better to make a solder coverage. this board will be large..

Thank-you for helping me. If there is any other suggestion please tell me

 

[NIKHILRAJ]

if possible go for a bus bar ( additional metalic strip) since your power requirement is little bit high.

will BTA26 meet the clearance requirement for 230v

 

[andre_luis]

...if possible go for a bus bar...

For specified current of 15A it is not necessary...
Even for a greater rating of 40A I already used with a BTA41, track metalization is quite enought.


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[Mattylad]

Goto Google, search for Saturn PCB Design and PCB tools.

A brilliant utility for working out track currents et all.

 

[NIKHILRAJ]

For specified current of 15A it is not necessary...
Even for a greater rating of 40A I already used with a BTA41, track metalization is quite enought.


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just put forward a suggestion ... it may help to reduce the PCB size...now a days everything is becoming smaller even thr man mind !!!:sad:

 

[andre_luis]

...it may help to reduce the PCB size...now a days everything is becoming smaller...

This procedure requires a human handled assemblyng step, which reduces an automation attribute of this design to equipment manufacture.
Other probem at a metalic bar is the susceptibility to bad contacts due to mechanical shock.

As I said this amount of current is not critical...


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[yoannes]

Hi,

I made the board with no mask..

I don't know if this post should continue here. But I have another doubt.

I made a board really simple with this TRIAC and I wanted to add an current sensor for me to monitor and turn off the TRIAC if I get some overload.
The problem is I cant find any sensor that can be used with the board, I find only the ones witch have to pass the cable through.. Is there any sensor that can be added to the board?

 

[FvM]

A pass-through current transformer can be still used with a jumper wire. Otherwise, look for Allegro ACS7xx hall effect current sensors.

 

[yoannes]

Hi,

Thank-you, that solved my problems!!!