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PCB design to drive a 36V,78A DC motor

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haddaji

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goodmorning, i am tasked with designing a PCB to drive a DC motor in différent speeds.
my one problem is what kind of PCB/wire track thickness to use so that my PCB could withstand that much current without damaging it? any ideas?
PS: it's a buck converter with an IRFP064N mosfet.
 

ronsimpson

Well-Known Member
Most Helpful Member
Most companies that make PCBs have a calculator for trace width and current. Go to their web page.
For two sided PCB the calculation is easy. You will need to know copper thickness.
For 4 layer; the inside layers heat up faster so less current.
 

Awesome Academy

New Member
Hi
78 Amps is a hell of a lot of current... I would recommend at least a 4 oz/ft^2 thickness copper PCB. You could use an online calculator like this to estimate the change in temperature for different trace widths. You are going to want VERY thick traces, as wide as possible.
I'm also a bit confused about your design. You say you want to control a DC motor but you plan on doing it with a buck converter? You don't want to be using a buck converter to control the speed of a motor. If you want to control the motor in one direction you could use a MOSFET switch on the low side of the motor. If you want bidirectional motor control you will want an H bridge circuit.
 

haddaji

New Member
first of all thanks for the replies.
Second,for [email protected] academy a buck converter delivers an output voltage that is lower than the input voltage depending on the duty cycle. for a duty cycle varying from 0 to 1 , i will have différent RPMs.
knowing this , i began my design but différent calculations like copper thickness, junction temperature rise,inductor filter size etc were not realistic at all. i began researching and now i am considering a 2 phase synchronous buck converter wich, so far, has offered me better results (calculations). I hope that i cleared some confusion for you , and thanks again .
 

alec_t

Well-Known Member
Most Helpful Member
a buck converter delivers an output voltage that is lower than the input voltage depending on the duty cycle
Understood. So are you planning to vary the output voltage to control motor speed? That is not the best way. Why not use conventional PWM?
 
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