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Power Electronic in pcb designer doubt

Didan , 05-01-2019, 11:13 AM
Dear forum, one friend send me a question and I dont have sure if there are other options, solutions for his problem. Well he sent me his layout, attached here and asked me: "The voltage is 12v and 900w power with a current of ~ 80A. Do you know if you can do everything on the same Board without needing a Track width of 224mm to 25mm in length? The current will be delivered to the Motor by PWM, and its operating time will be 5 sec. every 10min." So my answer was that if I wanna to deliver 80A for a motor I need to size the track for 80A, this way I can deliver full pwer for motor, but Im not expert in power electronics systems and I wanna to know from this forum, what others experience PCB Designers have to say, like use a specific electronic device or solution to avoid use very very wide track on his board. Thanks.

The following link is for the motor he wants to power:
Os Guincho Elétricos 12v da linha NAGANO são perfeitos para trabalhos de locomoção na horizontal. São robustos e potentes.Um equipamento indispensável para jipes, trollers, quadriciclos, que podem ser utilizados também em carros. Proporcionam praticidade e facilidade sem ter qualquer esforço desnecessário, sem contar que poderão ajudá-lo a sair de um atoleiro mesmo com o veículo desligado, já que contam com sistema de energia 12v. Motores variam de 01HP a 06HP e que suportam de 3000LBS a 20000LBS (Consultar especificações de acordo com seu modelo). Tenha o melhor do Off Road no seu veículo. 
Paul van Avesaath , 05-02-2019, 05:39 AM
use very wide tracks.. in anycase go as wide as you can.. or better yet add 2 internal plane and use that..
robertferanec , 05-03-2019, 07:09 AM
I am not expert for high current applications, but still maybe this will help:

1) First, be sure you filter this circuit properly - if not filtered properly, big currents can cause EMC/EMI problems

​2) as @Paul van Avesaath mentioned, there are different techniques for high current delivery - one of them is to route same track on multiple layers in parallel. Also, be sure you use thick copper (when choosing PCB stackup, instead of using standard 1oz thick copper, you may want to go for something thicker e.g. 2oz). Possibly there are other techniques e.g. add solder / tin layer on the tracks, create aluminum PCB, etc. But 80A should be ok with tracks routed on multiple layers in parallel.
Derek , 05-04-2019, 12:30 PM
Hello Didan,

What you are showing in the pic of your layout will not work. At least this is not high voltage!

Robert has made good recommendations to get you going.

I say "you" in my questions here because your friend wants your opinion.

Here are a few things to consider:

- Are you using a trace width calculator like the Saturn toolkit?

- What are the connector pins rated at?

- You are showing thermal relief spokes on the connector. Generally speaking this is what we want, but to determine how much current you can handle you have to get the total cumulative copper web and you may be surprised those spokes won't be able to handle that much current. IPC-2222 covers this well. There have been a few occasions where I flooded the pin with copper because not enough trace width on the spokes. I don't recommend this because it can be very difficult to ever rework if necessary. The manufacturing people may not like you very much for this. Plus it's going to take more heat to even get those pins soldered. But we did it and it worked! One board was 60 amp.

- Is this a commercial product? Just want to make sure it doesn't need to meet high reliability requirements which can make things more difficult for you in areas.

- Will this board need to have documentation to show what IPC classifications it needs to meet?

- What board material? FR4 is always thrown out there because of it's common use, but there are multiple FR4 materials with different ratings and some can handle higher temperatures etc.

I have used higher copper weights than 2 Oz but it will add cost etc. But plan on at least 2 Oz

I will be happy to help you with anything else on high power


Didan, 05-15-2019, 02:52 PM
Hi Derek, thanks to share your experience =D
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