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I have a project where I need to power two 5V 40A loads. To save space, I'd like to power them off a single power supply module, something like this power supply [pdf].

The PSU supports remote sense to detect voltage drop. I don't know how I would connect the remote sense across both loads - so I guess it would just go across one?

The power supply has short-circuit protection, but 5V 90A is still quite a lot of power. Should I include a 50A fuse in-line with each load? Or is the short circuit protection enough?

If I have a fuse in-line with each load, and the fuse blows, this article makes it sound like the current will flow through the remote sense lines, but doesn't suggest any solutions. How should I prevent this?

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    \$\begingroup\$ Remote sense lines are usually relatively high impedance in order to keep the current down to a minimum. \$\endgroup\$ – Ignacio Vazquez-Abrams Nov 6 '17 at 17:25
  • \$\begingroup\$ Short circuit protection is protecting the PSU. Fuses inline with the load might protect the load. \$\endgroup\$ – Eugene Sh. Nov 6 '17 at 17:27
  • \$\begingroup\$ Fuses protects the wiring harness, so you might use a fuse if the wire cross section is smaller than PSU can output. \$\endgroup\$ – Marko Buršič Nov 6 '17 at 17:31
  • \$\begingroup\$ What is your power supply? A well designed one should sense if the remote sense is supplying a non negligible level of current and shut down. This may be as simple as having PTCs in series with the sense lines so these get hot and can not provide any significant current or may measure the voltage difference between the output terminals and the sense leads shutting the unit down if it is two much say 1V. \$\endgroup\$ – Warren Hill Nov 6 '17 at 17:40
  • \$\begingroup\$ @WarrenHill - the power supply I'm evaluating is linked above. It's a Meanwell HRP-450-5 \$\endgroup\$ – MattE Nov 6 '17 at 18:20
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Since the PSU has fixed current limiting protection, the wire must withstand 50A to each load. More important the voltage drop must be acceptable if the loads are not matched. You can always combine with suitable resistors and separate sense wires. But also recognize it must be done with the return wire as well.

This maym force you to use a wire gauge with considerably larger Amapacity if it is long. Use AWG tables to estimate the voltage drop on each wire.

Also try to use twisted wire to reduce CM noise.

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Do you need remote sense? You could use large cables to connect your 5V, then jumper the remote sense to output of the supply before the fuse. In this way, your voltage drop would be minimized, and no need for remote sense.

Also, you could put the remote sense before the fuse, and keep the lines very short post-fuse to the load.

Do you need a fuse? Your supply can only put out 90A, and your loads each pull 40.

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  • \$\begingroup\$ Thanks. I don't need remote sense, but if the PSU offers it, it would be nice to use instead of manual calibration. Putting remote-sense before the fuse is a nice idea! \$\endgroup\$ – MattE Nov 6 '17 at 18:25

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