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“Why does a car like the Tesla still have old-style fuses?”
61–70 of 72 posts
Re: “Why does a car like the Tesla still have old-style fuses?”
#62Short answer (pun only somewhat intended): interrupting high-current DC is not as straightforward as it looks. For instance, deactivating a set of relay contacts tends to cause an arc if any amount of current is being interrupted (inductive loads make this worse). For AC, this is manageable since the waveform will hit a zero-crossing in a a handful of milliseconds worst-case, terminating the arc. For DC, no such luck. In extreme cases, the arc can actually WELD the contacts together.
Fuses will, barring ludicrous overload (putting a 12V fuse in a 10kV DC circuit), fail open - a definite positive for a safety measure.
Using fuses makes sense in a lot of applications because they are (as noted above) safer, cheaper, and more reliable. It probably doesn't hurt that a fuse is easier to diagnose; control circuits can intermittently fail but an "intermittently blown" fuse would be an odd thing indeed.
Re: “Why does a car like the Tesla still have old-style fuses?”
#63I think its because fuses don't blow in a car because you plugged in one too many things. They tend to blow because there is something that needs to be fixed. Maybe circuit breakers make it too easy to ignore serious problems.
Re: “Why does a car like the Tesla still have old-style fuses?”
#64"What's the problem?" "Car won't start." "Did you try restarting it?"
No joke, I have seen a car which would occasionally refuse to start (with no indication of an error: the dash was basically blank) until you disconnected the battery, waited a few minutes, and then reconnected it.
Disconnecting the battery and waiting is how to clear the fault flag on ODB-1 era GM cars/trucks (at least, probably others as well.) And if you short two pins on the ODB connector, then power on, it will flash trouble codes on the check engine light.
And apparently some of them have 160 or 8192 baud serial on that connector, with really expensive cables, unless you're handy with an arduino or similar. Now that the truck is working, I'm not sure I need to do this... yet.
Re: “Why does a car like the Tesla still have old-style fuses?”
#65Earlier quoted context omitted.
The British plug is a marvel of good engineering. Other countries look on it with envy (except possibly Australia, which has a similar design of its own, IIRC). Now of course it was "overengineered" by the standards of the time, to compensate for our ludicrous, dangerous, and still-legally-required "ring main" system, which as you say was due to aftermath-of-WW2 copper shortages. But the plug design is the part we go…
Australian plugs are good, but have the live pins at the top (so for example a dropped coin will balance across them and short when the plug is pulled out), the plug doesn’t have its own fuse and the socket isn’t shuttered with no plug inserted.
I dare you to try to plug an australian plug in the dark.
It's just impossible ! Most other plug make it way easier .
Re: “Why does a car like the Tesla still have old-style fuses?”
#66Because cars are not expected, under normal circumstances, to experience abnormal amounts of current on any given circuit. Unlike a house, where you can easily plug in something into the outlet that can overwhelm the circuit, in a car each circuit is designed specifically for a given maximum load. When you blow a circuit in a house, you have most likely massed up and plugged too many things into one outlet, or your d…
> These components are not expected to fail, even though they often do. Don't believe me, talk to any mechanic. However, because they are not expected to fail, they are often installed deep inside the car. So, now, if your headlight module fails, it costs $400 in parts, and several hours of labor to fix the same problem. Progress? Hell, when the HEADLIGHT BULB fails, which is something that IS expected to happen, it…
This is an odd place to give car repair advice, but since I just did this job today on my wife's 2005 (same car), I have to say its one of the easiest headlamps I've done. 5 mins total for a low-beam. If the latch were reversed, it wouldn't hold itself out of the way when inserting the new bulb. You'd be trading one problem for a worse one, IMO.
Should you need to do a high-beam, you may need to pull the battery on the (US) driver side, or the power steering reservoir on the other side. The PS bottle comes right off (no tools, IIRC), so it's only the one high beam on left side that's particularly tough.
Re: “Why does a car like the Tesla still have old-style fuses?”
#67Well, even planes use CB today instead of fuses (and remote CBs on top of that, meaning they can be turned on/off electronically) I think WOZ is suggesting an active current control that, while doable, is probably too risky (and you really don't want to blow the expensive parts)
> Well, even planes use CB today instead of fuses (and remote CBs on top of that, meaning they can be turned on/off electronically) If you have something drawing too much current in a plane, and so it is a fire risk, it still might be overall safer to continue to use it. For instance, if it is something involved in lowering the landing gear you might decide it is safer to risk a small fire in order to get the gear do…
Pilot (of smallish airplanes) here. Landing gear failures are almost never fatal unless they make the crew mismanage the airplane into a crash. (Eastern 401 or the one in the Bahamas last month (C6-REV) where the press is hailing the pilot a hero for only killing 1 pax, when the reality is no one should have gotten hurt or even wet if properly handled.)
For an important item, I'll reset a breaker once in flight. Nothing electrical is that critical, and I carry portable AHRS, GPS, and handheld VHF radio.
Few things are worse than fire, so if I have any concern about the electricals, they can all stay off and I'll extend the gear manually with the crank system. Other planes have gear that free falls or has an N2 bottle to blow the gear down.
I don't think any civilian aircraft have had fatalities from a simple gear-up landing.
Re: “Why does a car like the Tesla still have old-style fuses?”
#68Earlier quoted context omitted.
The British plug is a marvel of good engineering. Other countries look on it with envy (except possibly Australia, which has a similar design of its own, IIRC). Now of course it was "overengineered" by the standards of the time, to compensate for our ludicrous, dangerous, and still-legally-required "ring main" system, which as you say was due to aftermath-of-WW2 copper shortages. But the plug design is the part we go…
Ring final circuits aren't legally required, you can use exclusively radials if you prefer. The cost is of course thicker cables for the same power rating, and so in most domestic installs it is still more economical to use ring circuits. What makes you think ring circuits are dangerous? Incompetent installation?
Wikipedia lists quite a few potential problems with ring circuits. I don't know how valid these complaints are.
https://en.wikipedia.org/wiki/Ring_circuit#Criticism
Re: “Why does a car like the Tesla still have old-style fuses?”
#69Earlier quoted context omitted.
Australian plugs are good, but have the live pins at the top (so for example a dropped coin will balance across them and short when the plug is pulled out), the plug doesn’t have its own fuse and the socket isn’t shuttered with no plug inserted.
So Australian plugs are a bit like UK ones except upside down? :-)
Except the Australian plugs look like one of the masks from Scream or Scary Movie or something.
Evidence: Socket: http://i.imgur.com/zwRYC25.jpg Mask: http://i.imgur.com/b0RAZ9k.jpg
Re: “Why does a car like the Tesla still have old-style fuses?”
#70Earlier quoted context omitted.
On the point about building wiring codes, here in the UK we actually do have both central fuses/circuit-breakers and load specific fuses in the plug for each device. After reading your comment it did make me wonder as I plugged our coffee machine this morning how the design substantial chunk of plastic and metal I was holding was influenced by the aftermath of WW2.
The British plug is a marvel of good engineering. Other countries look on it with envy (except possibly Australia, which has a similar design of its own, IIRC). Now of course it was "overengineered" by the standards of the time, to compensate for our ludicrous, dangerous, and still-legally-required "ring main" system, which as you say was due to aftermath-of-WW2 copper shortages. But the plug design is the part we go…
> Other countries look on it with envy
We really, really don't. The most charitable of us manage to appreciate it as a quaint example of British discomfort, like those sinks with separate boiling/freezing water taps at opposite corners.