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  #11  
Old 01-30-2010, 05:58 AM
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Jimdear2 Jimdear2 is offline
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Default Re: Source for Emergency Disconnect Switch

Jack,

What most people seems to be missing is that the idea behind an emergency stop is it is for EMERGENCIES.

This should be something that everyone recognizes and even a child can be taught to use.

It should be placed where everyone can see it It shouldn't be hidden or complicated or require more the one simple move to operate.

Quote:
Originally Posted by jackbauer View Post
I used a kilovac ev200 main contactor. Rated to open once at 320v 2000amps. So if something happens i just switch off the key. Job done.
Jack,

That will work as a standard disconnect. The important information here is the Open Once specification of the contactor.

Quote:
Originally Posted by jackbauer View Post
If you wanted to be 110% just use a second kilovac connected to a normal nc industrial emergency stop button placed on the dash or nearby. I got mine for $75usd.
The Big Red Button connected to a contactor idea is even better. After all you don't want the guy who is peeling you out of a burning car to hesitate while looking for a emergency battery disconnect.

Although, I personally, prefer a mechcanical emergency disconnect, thats just one of my quirks. I use my tractors in compitition and I wrote (am writing) the rules for the classs, so mechanical disconnects are required.

For those of you building cars or trucks, there are international standards for battery pack disconnects that are recognized by emergency service personal. They are trained to use them to protect themselves. You should investigate those rules see if they apply in you locality.
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Last edited by Jimdear2; 01-30-2010 at 06:12 AM. Reason: As usual speeling <grin>
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  #12  
Old 01-30-2010, 08:15 AM
green caveman green caveman is offline
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Default Re: Source for Emergency Disconnect Switch

Jim,

I'm with you on this one. I've pushed a few E-Stops in earnest in my life, once when my finger was caught in a belt, and been very glad that they were there, accessible, and worked.

Quote:
Originally Posted by Jimdear2 View Post
It should be placed where everyone can see it It shouldn't be hidden or complicated or require more the one simple move to operate.
I've built industrial equipment where you have two start buttons at arms length on each side of the machine - this means the operator can't have their hands in the machine when it starts.

You still need an accessible E-Stop and, with the hands occupied, that leaves you with few body parts to hit it with. The primary choice was to place it so that with a flex of the hips you could hit the big red button.

Quote:
Originally Posted by Jimdear2 View Post
That will work as a standard disconnect. The important information here is the Open Once specification of the contactor.

The Big Red Button connected to a contactor idea is even better. After all you don't want the guy who is peeling you out of a burning car to hesitate while looking for a emergency battery disconnect.
I don't think that the "Open Once" contact is a good idea. You wouldn't what to hesitate because after you hit it the car won't run/time to repair/whatever. If something's going wrong, or you suspect that something's going wrong - hit the E-Stop.

Quote:
Originally Posted by Jimdear2 View Post
Although, I personally, prefer a mechcanical emergency disconnect, thats just one of my quirks. I use my tractors in compitition and I wrote (am writing) the rules for the classs, so mechanical disconnects are required.
Most safety specs require E-Stops to be mechanical. I've had people suggest that you run an E-Stop through a PLC or computer control, which is not allowed (and a bad idea).

As far as I know, knife switches are used to connect/disconnect under load. So it should be possible to find one that is designed to disconnect while loaded and rated for enough amps.

I haven't found an industrial E-Stop with high enough current rating. If someone has link/part number that would probably be a good source.

I still don't really know how I feel about the mechanical and electrical contactor being the same. If the stories about potentially welded contacts are true, I'd want to be sure that the E-Stop and the normal closure are not the same contacts. But that may be a little more paranoid that I need to be.
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  #13  
Old 01-30-2010, 08:23 AM
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Default Re: Source for Emergency Disconnect Switch

I'd love to be able to buy a true ev emergency disconnect. My issues is that what we are all afraid of is a failed controller going full on. Should that happen the current will be very very high. Any of the so called emergency switches I have seen on this and other threads will turn into a plasma ball if opened under serious load. Don't believe me? Buy one and connect it to an industrial dc arc welder wind it up to 500amps and hit the switch.!!! Be sure to take precautions and post a video. And thats only about 50v max!

I accept the points made not trying to be argumentative just pointing out that whats available on the market is just not suitable. Just today i was messing about powering the shunt field on my motor from 48v. Only draws 2 amps at that voltage. Disconnected the wire from the battery and drew a 1 inch arc!
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Old 01-30-2010, 08:33 AM
green caveman green caveman is offline
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Default Re: Source for Emergency Disconnect Switch

Quote:
Originally Posted by jackbauer View Post
I'd love to be able to buy a true ev emergency disconnect. My issues is that what we are all afraid of is a failed controller going full on. Should that happen the current will be very very high. Any of the so called emergency switches I have seen on this and other threads will turn into a plasma ball if opened under serious load. Don't believe me? Buy one and connect it to an industrial dc arc welder wind it up to 500amps and hit the switch.!!! Be sure to take precautions and post a video. And thats only about 50v max!

I accept the points made not trying to be argumentative just pointing out that whats available on the market is just not suitable. Just today i was messing about powering the shunt field on my motor from 48v. Only draws 2 amps at that voltage. Disconnected the wire from the battery and drew a 1 inch arc!
Good point. So the E-Stop should be rated at least as highly as the fuse in the circuit. If you have a 500 Amp fuse, you need a 500 Amp+ disconnect.

Do arc welders have E-Stops?
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Old 01-30-2010, 08:36 AM
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Default Re: Source for Emergency Disconnect Switch

Quote:
Originally Posted by green caveman View Post
Good point. So the E-Stop should be rated at least as highly as the fuse in the circuit. If you have a 500 Amp fuse, you need a 500 Amp+ disconnect.

Do arc welders have E-Stops?
No i was just being a smart ass! What I should have said is that to test that a switch can break a dc circuit under load connect it to the output of a dc arc welder , turn the welder on then operate the disconnect. Typical arc welders run about 50v dc on no load so if it cant break that power safely its useless at high ratings.
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  #16  
Old 01-30-2010, 09:07 AM
green caveman green caveman is offline
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Default Re: Source for Emergency Disconnect Switch

Quote:
Originally Posted by jackbauer View Post
No i was just being a smart ass! What I should have said is that to test that a switch can break a dc circuit under load connect it to the output of a dc arc welder , turn the welder on then operate the disconnect. Typical arc welders run about 50v dc on no load so if it cant break that power safely its useless at high ratings.
No, I understood the first time. I was just hoping that disconnect was required in the high-amp low voltage side that would work for an EV.

Solar installations have high amp disconnects, but they are pretty expensive. I think that they are typically breakers, just like the 15A home circuit breakers but 300A+.
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  #17  
Old 01-30-2010, 02:16 PM
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Default Re: Source for Emergency Disconnect Switch

I know not everyone can do it (because of choices and design), but it's also a good reason to have a clutch. The clutch can disconnect the motor from the drivetrain, and just doing that will reduce current to the point where something like a contactor or Anderson disconnect should work without welding, imo.
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  #18  
Old 01-30-2010, 02:35 PM
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Default Re: Source for Emergency Disconnect Switch

Probably something wrong with this thought but...

There is a main fuse that should be able to break safely at over load current.
Could an emergency shut off simply put a dead short in the circuit to force the fuse to blow?
To reset the break just open the circuit and replace the fuse.
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  #19  
Old 01-30-2010, 03:28 PM
green caveman green caveman is offline
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Default Re: Source for Emergency Disconnect Switch

Quote:
Originally Posted by Overlander23 View Post
I know not everyone can do it (because of choices and design), but it's also a good reason to have a clutch. The clutch can disconnect the motor from the drivetrain, and just doing that will reduce current to the point where something like a contactor or Anderson disconnect should work without welding, imo.
Or put it into 5th and hope you blow the fuse? I might think of the clutch, but I doubt that my son would - at least until he has some more driving experience. Then turn the key while the motor is trying to shake the itself to bits - that's all pretty scary?

To keep it in perspective, there are many ways to kill or injure yourself on the road, in EV's or ICE. Many you have no control over. You need a succession of failures, runaway, welded contactor, fuse doesn't blow, forgetting the clutch, etc. for the E-Stop to become important (or at least the Amperage of the E-Stop to be important). So it's not a very likely condition.

It's just that, since you can buy a electrical contactor for ~$70 I would have expected that a simple (but high current) mechanical switch would have been available for under $100. The most cost-effective choice does seem to be the Curtis/Albright combined contactor/E-Stop, but that brings power into the cabin and might still have a problem if the contacts are welded.
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  #20  
Old 01-30-2010, 05:47 PM
DC Braveheart DC Braveheart is offline
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Default Re: Source for Emergency Disconnect Switch

I'm going to show my ignorance here ... in a runaway situation your controller has failed in such a way that it's not pulsing the voltage to the motor and your full pack voltage is going into the motor, right? In that case, as your motor tries to reach it's max speed (which is limited by the pack voltage) doesn't the backward EMF created by the increased speed cause the current to drop? I think that's why a motor's torque drops after a certain speed (since torque is proportional to current). So with less current flowing a contactor or other physical disconnect is less likely to weld itself if (when) it arcs when you open it if the motor is running away?
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