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Unread 12-02-2009, 11:19
ErichKeane ErichKeane is offline
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Re: Solving static electricity problems by grounding the frame

Vehicle fires are most often caused by heat hitting exposed fuel, not electricity. I don't seem to be able to find anything that says one way or the other, but of the ones I've dealt with and know of, they are all caused by fuel (other than in a direct collision, where positive is shorted to ground).

In my limited experience with the Prius, I have found that the body is used as a ground as well, though I'm not sure its the positive to the batteries as you say.

Quote:
Originally Posted by Mike Betts View Post
Erich,

I once had a good friend who worked at Bell Labs back in the early seventies. One of the quotes of his I always loved was "The nice thing about standards are that there are so many to choose from."

"Double isolated" appliances and systems do exist. Many hand power tools boast full isolation from earth ground and are usually designated Class 2 (see this Wikipedia entry).

In addition, the "grounded frame" exists for low voltage car systems only. In electric vehicles, hybrid vehicles, and (one of my development jobs before I retired) fuel cell vehicles, the high voltage system is always double isolated.

Lastly, do not confuse legacy systems such as the automobile with "safe" systems. There are literally thousands of vehicle fires every year. I did some research about a decade ago and the number for non-crash related vehicle fires was about 4,000 per year in the US alone. I just did a quick Google and found this for crash related fires.

Regards,

Mike