# High voltage fuses and contactors



## enp13 (Mar 26, 2009)

Has anyone had any experience sourcing high voltage DC fuses and contactors? My planned high performance conversion will have a battery pack open circuit around 800V and peak current 400A (Seimens AC motor) so that's a fair challenge to break in an emergency situation. The cheapest suitable contactor I can find is the Gigavac GX16 (breaks [email protected] 10 times). A borderline alternative would be the Tyco EV600 (breaks [email protected] twice). Both are easily available from various EV suppliers. But is there some other contactor commonly used for high voltage packs that I don't know about?

When it comes to high voltage DC fuses I have not found anything at all.


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## Nabla_Operator (Aug 5, 2011)

difficult to find a high voltage DC fuse:

The fuse is rated to blow at a certain current. Disregarding at which voltage level the fuse is working. The voltage over the fuse is zero. The fuse doesn;t know if it is located in the HV area of the circuit or in the zero voltage part of the circuit. 

It is just a matter of insulation. So: if you build in a 400 A fuse your own way... very well insulated from its environment.... it should even work with a 12Volt 400Amp fuse. Right?


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## frodus (Apr 12, 2008)

Just use an EV200... you should never open the contactor under load. If you are using an AC controller worth anything, it will likely control the contactor, so it'll cut current before opening the contactor.

And if you DO need to open it in emergency, you only need to open it once. IIRC, the EV200/LEV200 series will open like 2000A and work up to like 900VDC .... one time.


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## Brute Force (Aug 28, 2010)

> The fuse is rated to blow at a certain current. Disregarding at which voltage level the fuse is working. The voltage over the fuse is zero. The fuse doesn;t know if it is located in the HV area of the circuit or in the zero voltage part of the circuit.
> 
> It is just a matter of insulation. So: if you build in a 400 A fuse your own way... very well insulated from its environment.... it should even work with a 12Volt 400Amp fuse. Right?


*NO!!!*

*NEVER use a fuse not rated for your system voltage*. In the event of an overcurrent condition, the fuse element will vaporize but the plasma trail left in its place will continue to conduct and quite possibly never break the circuit. The fuse will then quickly overheat (think arc welder) and start melting things around it or start a fire. High voltage fuses are designed to have a gap large enough to quench the arc left after the link has evaporated. DC is a particular problem in that, unlike AC, the current does not cross zero on a regular basis.


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## dougingraham (Jul 26, 2011)

Nabla_Operator said:


> It is just a matter of insulation. So: if you build in a 400 A fuse your own way... very well insulated from its environment.... it should even work with a 12Volt 400Amp fuse. Right?


Nope. If it isn't designed correctly the fuse will open and the current will just jump the gap. A 12Volt DC 400A fuse may open when presented with more than 400 amps at say 800 volts but the 800 volts changes everything.

This probably belongs in the Technical Discussion section.


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## PStechPaul (May 1, 2012)

You might search for high voltage DC fuses for solar installations. Cooper-Bussman has some rated over 1000V and 600A, but they are probably several hundred dollars:
http://www.cooperindustries.com/con...lectrical/products/supplemental/pv-fuses.html

A 200A 600VDC RK5 fuse is about $163:
http://www.mouser.com/ProductDetail...=sGAEpiMZZMsIz3CjQ1xegWj74L0In0Np7VF6Fh81cwI=

The PV-160A-01XL 160A 1200V fuse is $436:
http://www.newark.com/cooper-bussmann/pv-160a-01xl-b-12/fuse-160a-1200v-1-xl-pv-bolt-in/dp/75T4552

You can use multipole contactors in series to get a higher voltage rating, and it may also work for fuses, but you should check with a qualified applications engineer to make sure. Here is what a 175A DC arc flash looks (and sounds) like:


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## evmetro (Apr 9, 2012)

Wow! That video was amazing! Does that arcing have anything to do with the speed that it blows, or is that purely from the wrong type of fuse?


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## PStechPaul (May 1, 2012)

The video mostly shows the worst case scenario of what can happen if an arc occurs. When contacts open slowly, a fairly low voltage arc will start, and then as they separate, it will increase in power as a plasma forms from vaporized contact material. This is essentially what happens when welding, but this arc has much greater power (because of higher voltage) than the usual arc welders. There are ways to handle the higher voltage arcs, which include much faster contact opening, magnetic arc suppressors, and insulating arc chutes which force the arc around a longer path. Fuses work a little differently from contactors and circuit breakers, and may use multiple points of opening and silica (sand) which absorbs energy and melts and makes an insulating barrier, while the casing keeps the arc from entering the environment where it can cause more damage.

At least that is my understanding of the mechanisms of fuses and contacts used to break high current. There is probably much more to it, and that is why so much design effort and testing are required for high power protective devices, and why they cost so much. A large part of the cost is also probably liability insurance, as the consequences of a fuse failure can be catastrophic and the manufacturer may be held liable for damages if it can be proven that the device failed when used within its advertised specifications. There are only a few really reputable manufacturers, but many "knock-offs" that are much cheaper. But it's difficult to get compensation from a random company in China.


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## gunnarhs (Apr 24, 2012)

dougingraham said:


> Nope. If it isn't designed correctly the fuse will open and the current will just jump the gap. A 12Volt DC 400A fuse may open when presented with more than 400 amps at say 800 volts but the 800 volts changes everything.
> 
> This probably belongs in the Technical Discussion section.


I agree with that. I had a case in a DC car where we (as novices) tried to use a 12V 100A relay for a case where the DC-Voltage was 30V and current 10A. It worked at first but after 10 times the contactors did not open. I opened the relay and the contacs were literally "welded" together. Amazing what a few dozen volt difference can do...
Contactors are of course more robust than relays but after this experience I use only appropriate stuff. Yes, that is expensive... (100 USD +)


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## Stefan6874 (Nov 23, 2013)

Thanks for sharing.
___________________________________
http://www.nutribulletrecipebook.com/


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## dragonsgate (May 19, 2012)

There are things you can take shortcuts on to save a few bucks but not something as safety related as fuses. I have had good luck with these guys. Intermountain Fuse Supply INC. phone 1 800 246 8336 or 1 801 486 8333 WWW.intermtnfuse.com


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## enp13 (Mar 26, 2009)

Thanks for all your comments. I can report some recent success:

*Fuses

*The Cooper Bussmann FWJ series, although nominally an AC fuse, are rated to break 25kA at 800V DC. 

http://www.cooperindustries.com/con.../products/high_speed_/north_american/fwj.html

I got mine here with mounting base ends for US$25 each:

http://www.ebay.com/itm/Cooper-Buss...4D-/170989972985?ssPageName=ADME:L:OC:US:3160

*Contactors*

The new Gigavac GV200 contactors have leaped ahead of anything Tyco offers. Will break 400A 750V DC 600 times and the datasheet lists many other combinations too. The coil economiser means zero back EMF and a staggeringly low 1.6W power consumption.

I got mine from here for US$115. They can also order in the 48V coil one for the same price if you want that for some reason:

http://www.evwest.com/catalog/product_info.php?manufacturers_id=25&products_id=273


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