PCB Fuses

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I'm looking for a PCB fuse. The voltage I'm working with is +48Vdc and I'm not 100% on breaking current just yet but it'll be somewhere between 10A - 15A. Ideally it should be something not particularly large (something like this would be ideal except the actual fuses only go up to 32V despite the holder being able to withstand 125V) and also something pretty standard, like one of the automotive blade fuses, as the end application will be mass produced meaning if the selected fuse were to go obsulete or something I'd have to change the design, where as a standard type of fuse could be replaced easily. 

Any suggestions welcome!

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Dc fusing is a challenge. If the load is somewhat inductive, then you need distance to interrupt the fault current. If the voltage source is batteries, then the fault current can be significant. This is due to an arc forming when the fuse blows and with DC, there is nothing to interrupt the current unlike AC where the current goes through zero 100 or 120 times a second. This is the reason for the voltage rating. Since telecoms is 48V, there should be plenty of solutions.

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If you don't need something in a socket then standard case sizes will always be available for example something from here:

http://ee.farnell.com/webapp/wcs...

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Kartman wrote:
Dc fusing is a challenge.

Yeah tell me about it, not quite as simple as it first might seem!

 

Kartman wrote:
Since telecoms is 48V, there should be plenty of solutions.

I wasn't aware of this, thanks for the tip! I'll look into that for sure.

 

bloody-orc wrote:

If you don't need something in a socket then standard case sizes will always be available for example something from here:

http://ee.farnell.com/webapp/wcs...

 

I was looking at SMD fuses, but I'd really like something with a socket of some form as should a fuse blow then our customers and/ or service engineers don't have to mess about with a soldering iron just to replace it. You can get sockets for SMD fuses though (I actually posted a link to one in my OP) so maybe I should persevere and keep looking along those lines - thanks for the suggestion!

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Kartman wrote:
If the voltage source is batteries, then the fault current can be significant. This is due to an arc forming when the fuse blows and with DC, there is nothing to interrupt the current unlike AC where the current goes through zero 100 or 120 times a second.
The logistics engineer told me he could see the arc during mate/demate; that was for a medium truck (24Vdc) application.

The solution was to de-energize the circuit (operator commands via electronics and software) before maintenance.

Kartman wrote:
Since telecoms is 48V, there should be plenty of solutions.
Sometime within the past decade, read an article about outlet boxes in 48Vdc data centers.

Senses current via the magnetic field strength.

Connector and circuit breaker all in the outlet box.

Break-before-make (no arc)

 

48V automotive - didn't know that's up and coming; not many, if any, protected FETs for it yet.

http://www.edn.com/design/power-management/4442279/Intelligent-power-switches-for-48V-battery-applications

Can get significant function (circuit breaker, over-volt, under-volt, etc) via one IC, a sense resistor (and such), and the FET :

http://www.linear.com/products/Surge_Stopper,_Overvoltage_*_Overcurrent_Protection

 

Photovoltaic - 48Vdc and then some (600Vdc and more).

http://www.littelfuse.com/products/fuse-blocks-fuseholders-and-fuse-accessories/dead-front-fuse-holders/lpsm.aspx

In quantity 10, the above is about 20USD each for the DIN-mount fuse holder and about 25USD each for the fuse.

The fuse forms are

  • Ferrule so could use an inexpensive fuse holder other than a safety concern due to arcing.
  • PCB mount via tabs; might consider a hot swap design where PCB with a blown fuse return via logistics.

 

"Dare to be naïve." - Buckminster Fuller

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Howard_Smith wrote:
... as should a fuse blow then our customers and/ or service engineers don't have to mess about with a soldering iron just to replace it.
The best I could do while searching for a resettable fuse :

http://www.mouser.com/search/ProductDetail.aspx?R=0virtualkey0virtualkeyRKEF500 (Resettable Fuses - PPTC 60V 40A 5.00W Radial-leaded Device, 5A hold, 10A trip)

 

"Dare to be naïve." - Buckminster Fuller

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Would it be a silly suggestion to put 2 fuses in series?

Note that the pdf from littlefuse you are refering to only goes upto 10A.

Doing magic with a USD 7 Logic Analyser: https://www.avrfreaks.net/comment/2421756#comment-2421756

Bunch of old projects with AVR's: http://www.hoevendesign.com

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Unfortunately, two fuses in series doesn't alter the voltage or current rating. It is unlikely both fuses would react at the same time, so one takes it for the team. In the case of a gross overload, one would blow, form an arc causing the next one to blow, forming an arc. Heat takes care of the rest.

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gchapman wrote:

The logistics engineer told me he could see the arc during mate/demate; that was for a medium truck (24Vdc) application.

The solution was to de-energize the circuit (operator commands via electronics and software) before maintenance.

 

That shouldn't be an issue in my case, the machinery will be turned off altogether for maintenance.

 

gchapman wrote:

48V automotive - didn't know that's up and coming; not many, if any, protected FETs for it yet.

 

If it is up and coming it's certainly not on my radar, as I mentioned in my OP all the automotive fusing solutions seem to only go up to 32V, which is a shame because a blade fuse would be ideal - in fact it's what I've used as a go to in the past (used 24V normally, only just stepped up to 48V for this project).

 

gchapman wrote:

The best I could do while searching for a resettable fuse :

http://www.mouser.com/search/ProductDetail.aspx?R=0virtualkey0virtualkeyRKEF500 (Resettable Fuses - PPTC 60V 40A 5.00W Radial-leaded Device, 5A hold, 10A trip)

 

I hadn't actually considered a resettable fuse, I normally use them on the lower voltages, typically logic level, but I've always used standard fuses for the DC supplies powering the entire hardware, mainly because if something goes wrong then it's easier to tell as the fuse will need to be replaced before anything will work again, unlike a resettable fuse which will come back to life! It's worth considering though, thanks for the suggestion!

 

Just for clarification here, am I right in thinking that should I use a fuse with a lower higher voltage rating than 48V, then should something go wrong and I end up with a dead-short across said fuse, that because I've exceeded the voltage rating it's not guaranteed to break? Essentially meaning my circuit wouldn't actually be protected, or are the risks associated with this far less dooming?

 

Thanks for the feedback and suggestions everyone

 

EDIT: correction

Last Edited: Tue. Oct 11, 2016 - 08:38 AM
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Voltage is one factor, fault current interrupting capacity is another..