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When to use fuses in circuit  


Active Member
Joined: 4 months ago
Posts: 6
2020-06-11 9:43 am  

I am working on a bench power supply. I posted the topic here: Link to My PSU project

Many designs used to adapt repurposed psu's I find on the web show added fuses. 

How do I determine when a fuse is needed and where to add it to the circuit?



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Reputable Member
Joined: 1 year ago
Posts: 325
2020-06-11 3:00 pm  


I usually add a fuse for just over my total current needs. Say I have a PSU that will deliver 20amps. I use only 4amps in total, so I will fuse the output for just over 4 or as close as I can.  Now, you may have a PSU that can only deliver 5amps and your circuit only nominally needs 3amps, BUT could pull more than 5amps in rare cases (i.e. a stalled motor)  I would put a 5amp fuse in to protect the PSU.  Now, for motors and motor controllers - You have a motor controller that can deliver 2amps max, but the stall of the motors is 3amps. You would want to fuse between the motor controller and the power source for just over 2amps.

I hope this makes sense.