# Contactor and Fuse for 3000 amps



## nimblemotors (Oct 1, 2010)

I'm wondering what safety disconnects are used in a car that can pull 2000 amps?


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## Yabert (Feb 7, 2010)

Since you are talking about car, I supposed that you talk about 2000 peak amps.
So, Gigavac GX110 1000 Ampere Contactor or, if your live has lower value , Dual GV200 Gigavac Contactor.


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## frodus (Apr 12, 2008)

Just be careful... what they fail to mention on EVWest, is that both contactors will NOT open at the same time. There are slight differences that would ultimately cause the full load to go through one contactor. They may do 6000A peak for 30s or 8000A peak, but they will NOT break that many amps. 

Breaking amps is still that of one contactor, because they actually do open at slightly different times. If you try opening 6000A, things will fail pretty spectacularly.... I can almost guarantee that. At 120VDC, you're looking at ~2200A breaking amps, for like 2 cycles before the contactor is a desk weight. At 350, you're looking at 1980A for 2 cycles. At 6000A, at any voltage, you could actually blow those contactors apart.

NEVER use two contactors to double the amp rating of a switch. Same reason you don't use two fuses in parallel to limit total current (unless you're splitting the load, like for 2 controllers).


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## Yabert (Feb 7, 2010)

Well explained Frodus!
It's why I've done a comment about low value life by choosing those contactors... there is chances that one don't open during an emergency case depending of current.


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## nimblemotors (Oct 1, 2010)

I agree that two contactors are not valid to double the BREAK ratings,
they would double the current flow capacity. 
For safety the issue is really the break ratings, and with a high voltage pack, if the controller dies, it could pump huge amps through the motor that you need to stop immediately.
I would disagree about fuses though, the current is not shared perfectly,
but it is shared, so when it is exceeded, one blows, then the other blows too.
A 300 volt 1000 amp fuse is very expensive, would not like to buy 4 of them.




frodus said:


> Just be careful... what they fail to mention on EVWest, is that both contactors will NOT open at the same time. There are slight differences that would ultimately cause the full load to go through one contactor. They may do 6000A peak for 30s or 8000A peak, but they will NOT break that many amps.
> 
> Breaking amps is still that of one contactor, because they actually do open at slightly different times. If you try opening 6000A, things will fail pretty spectacularly.... I can almost guarantee that. At 120VDC, you're looking at ~2200A breaking amps, for like 2 cycles before the contactor is a desk weight. At 350, you're looking at 1980A for 2 cycles. At 6000A, at any voltage, you could actually blow those contactors apart.
> 
> NEVER use two contactors to double the amp rating of a switch. Same reason you don't use two fuses in parallel to limit total current (unless you're splitting the load, like for 2 controllers).


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## frodus (Apr 12, 2008)

I disagree about the fuse, and here's why:

The first would blow, and then the second.... but the second would blow at 2X the amps arcing across it, which it is NOT rated for. If you properly choose the 1000A fuses, they may not explode.... but If you put 2000A through a 1000A that isn't properly rated, you CAN blow that fuse apart. Same exact thing with breakers. If one trips, the other one gets the full fault amperage across its contacts and it may very well blow up if used at 2x the rated current.

I've done many breaker/fuse/relay coordination studies... its not fun to see what happens at high currents like this. Used to work at GE Energy, same as my father who's the head of the power lab.

*Use one fuse, properly rated. Use one contactor, properly rated. Use one breaker, properly rated.*


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## z_power (Dec 17, 2011)

I wonder if there exists HV and hi current version of pyrotechnic "blowable link" used in +12V line in BMWs? It has very low cycle life of 1  but you don't need to switch off 3000A load very often...


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## kennybobby (Aug 10, 2012)

The Tesla pack has a big Bussmann 170MM4416 fuse with continuous current rating of 630 Amps and I2t of 52000. They use a special Tyco EVC500 contactor. Also use similar contactors in the high voltage junction box to switch between either AC or DC supply current for charging.


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