Importance of isolating the traction pack?

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Importance of isolating the traction pack?

Thor Johnson
How important is it to have the traction pack isolated from the chassis
ground?

 

I would think that step 1 to any work on the traction pack would be to
remove the main amp connector, then just be careful you don't drop a
wrench into the batteries (and to keep EMI from getting too large, the
packs should be designed with +/- paths as small as possible and exiting
near each other)...

 

Are most DC-DC controllers isolated?

 

 

Thanks,

Thor Johnson

 

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Re: Importance of isolating the traction pack?

Chris Zach
Thor Johnson wrote:
> How important is it to have the traction pack isolated from the chassis
> ground?

Depends. Would you care if a double-fault existed and blew up everything
on the 12 volt bus?

The Prizm has a 300 volt pack and ground fault detection. The reason is
if the pack goes to ground on one side it's a matter of time before it
goes to ground on the other. Then you have a nice 300 volt short in the
pack.

Or it goes to a line in the car, you touch it along with the frame and
die. Also kind of messy: I really like knowing where the dangerous stuff
is in my car.

Chris

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Re: Importance of isolating the traction pack?

Bill Dube
Since there is no "ground" on a car with rubber tires, you are forced
to "isolate and insulate" rather than "shield and ground."

On a stationary machine, you can connect the frame strongly and
relaibly to earth ground and make it nearly impossible for the frame
to have a lethal voltage with respect to earth ground. You can then
connect one leg of the power source to the same earth ground, if you
want to, because there is _nearly_ no chance of this causing the
frame to rise above earth ground to a lethal voltage. Since you are
able to, you choose the "conductive" approach to safety.

If you connect the traction wiring to the impossible-to-ground
chassis, there are many many ways for the chassis to have a lethal
voltage with respect to earth ground, particularly when it is on
charge. Thus, you do everything you can to prevent connection of the
traction wiring to the chassis and to isolate the traction voltages
from earth ground. Since you cannot use the "conductive" approach to
safety, you must choose the "insulative" approach to safety.

Bill Dube'

At 11:50 AM 1/26/2009, you wrote:

>Thor Johnson wrote:
> > How important is it to have the traction pack isolated from the chassis
> > ground?
>
>Depends. Would you care if a double-fault existed and blew up everything
>on the 12 volt bus?
>
>The Prizm has a 300 volt pack and ground fault detection. The reason is
>if the pack goes to ground on one side it's a matter of time before it
>goes to ground on the other. Then you have a nice 300 volt short in the
>pack.
>
>Or it goes to a line in the car, you touch it along with the frame and
>die. Also kind of messy: I really like knowing where the dangerous stuff
>is in my car.
>
>Chris
>
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Re: Importance of isolating the traction pack?

Matt Lacey
In reply to this post by Thor Johnson
For isolation, something else you should look into is putting a (or a few)
contactor(s) in the middle of your pack.

IIRC, The kelly DC controllers arent isolated.

Matt

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of Thor Johnson
Sent: Tuesday, 27 January 2009 3:32 AM
To: Electric Vehicle Discussion List
Subject: [EVDL] Importance of isolating the traction pack?

How important is it to have the traction pack isolated from the chassis
ground?

 

I would think that step 1 to any work on the traction pack would be to
remove the main amp connector, then just be careful you don't drop a wrench
into the batteries (and to keep EMI from getting too large, the packs should
be designed with +/- paths as small as possible and exiting near each
other)...

 

Are most DC-DC controllers isolated?

 

 

Thanks,

Thor Johnson

 

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Re: Importance of isolating the traction pack?

Bill Dube
No DC or AC EV controllers are isolated. (That I know of.)

At 05:07 PM 1/26/2009, you wrote:

>For isolation, something else you should look into is putting a (or a few)
>contactor(s) in the middle of your pack.
>
>IIRC, The kelly DC controllers arent isolated.
>
>Matt
>
>-----Original Message-----
>From: [hidden email] [mailto:[hidden email]] On Behalf
>Of Thor Johnson
>Sent: Tuesday, 27 January 2009 3:32 AM
>To: Electric Vehicle Discussion List
>Subject: [EVDL] Importance of isolating the traction pack?
>
>How important is it to have the traction pack isolated from the chassis
>ground?
>
>
>
>I would think that step 1 to any work on the traction pack would be to
>remove the main amp connector, then just be careful you don't drop a wrench
>into the batteries (and to keep EMI from getting too large, the packs should
>be designed with +/- paths as small as possible and exiting near each
>other)...
>
>
>
>Are most DC-DC controllers isolated?
>
>
>
>
>
>Thanks,
>
>Thor Johnson
>
>
>
>_______________________________________________
>General EVDL support: http://evdl.org/help/ Usage guidelines:
>http://evdl.org/help/index.html#conv
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>
>
>
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>Checked by AVG.
>Version: 7.5.552 / Virus Database: 270.10.10/1904 - Release Date: 20/01/2009
>7:49 AM
>
>
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Re: Importance of isolating the traction pack?

Bill Dube
Just to be clear, controllers are isolated pack-to-chassis, but not
motor-to-pack.

Is this what you are referring to?

Bill Dube'

At 05:16 PM 1/26/2009, you wrote:
>No DC or AC EV controllers are isolated. (That I know of.)

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Re: Importance of isolating the traction pack?

Mike Willmon-3
In reply to this post by Thor Johnson

As long as the motor fields are isolated from their housing (which I am
assuming most are unless it is a starter motor of sorts) then it still
keeps the pack isolated from the chassis.  Right?

On Mon, Jan 26, 2009 at  3:29 PM, Bill Dube wrote:

> Just to be clear, controllers are isolated pack-to-chassis, but not
> motor-to-pack.
>
> Is this what you are referring to?
>
> Bill Dube'
>
> At 05:16 PM 1/26/2009, you wrote:
>> No DC or AC EV controllers are isolated. (That I know of.)
>
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Re: Importance of isolating the traction pack?

Matt Lacey
In reply to this post by Bill Dube
I meant pack to chasis.

I remember some discussion a while back about blown up kelly controllers,
because the traction pack ground was on the wrong side.
I could of course not be remembering correctly.
I'll see if I can dig up the old discussion.

Matt

-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On Behalf
Of Bill Dube
Sent: Tuesday, 27 January 2009 9:29 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Importance of isolating the traction pack?

Just to be clear, controllers are isolated pack-to-chassis, but not
motor-to-pack.

Is this what you are referring to?

Bill Dube'

At 05:16 PM 1/26/2009, you wrote:
>No DC or AC EV controllers are isolated. (That I know of.)

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Re: Importance of isolating the traction pack?

CHARLIEP
In reply to this post by Thor Johnson

Thor Johnson wrote
How important is it to have the traction pack isolated from the chassis
ground?

 

I would think that step 1 to any work on the traction pack would be to
remove the main amp connector, then just be careful you don't drop a
wrench into the batteries (and to keep EMI from getting too large, the
packs should be designed with +/- paths as small as possible and exiting
near each other)...

 

Are most DC-DC controllers isolated?

 

 Would grounding the chassis to a reliable ground before  working on ev  give any protection? Charlie P

Thanks,

Thor Johnson

 

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Re: Importance of isolating the traction pack?

Cor van de Water
In reply to this post by Mike Willmon-3
Correct when the motor is clean.
DC motors in particular have a tendency to collect
a layer of conductive brush dust, so over time
there is an increasing path from motor windings
(brushes actually) to chassis.
When the leakage current gets too high then it is
time to clean the motor.

Regards,

Cor van de Water
Director HW & Systems Architecture Group
Proxim Wireless Corporation http://www.proxim.com
Email: [hidden email]    Private: http://www.cvandewater.com
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Tel: +1 408 383 7626        VoIP: +31 20 3987567 FWD# 25925
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-----Original Message-----
From: [hidden email] [mailto:[hidden email]] On
Behalf Of [hidden email]
Sent: Tuesday, January 27, 2009 6:20 AM
To: Electric Vehicle Discussion List
Subject: Re: [EVDL] Importance of isolating the traction pack?


As long as the motor fields are isolated from their housing (which I am
assuming most are unless it is a starter motor of sorts) then it still
keeps the pack isolated from the chassis.  Right?

On Mon, Jan 26, 2009 at  3:29 PM, Bill Dube wrote:

> Just to be clear, controllers are isolated pack-to-chassis, but not
> motor-to-pack.
>
> Is this what you are referring to?
>
> Bill Dube'
>
> At 05:16 PM 1/26/2009, you wrote:
>> No DC or AC EV controllers are isolated. (That I know of.)
>
> _______________________________________________
> General EVDL support: http://evdl.org/help/
> Usage guidelines: http://evdl.org/help/index.html#conv
> Archives: http://evdl.org/archive/
> Subscription options: http://lists.sjsu.edu/mailman/listinfo/ev

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