4 ms·

The argument sounds kind of persuasive to a layman (even one that did a little bit of EE a while back), but my gut says there would be no need to write this art

The argument sounds kind of persuasive to a layman (even one that did a little bit of EE a while back), but my gut says there would be no need to write this article if there weren't regulations or other engineering traditions that decided galvanic isolation is necessary for safety. I guess the difference is galvanic isolation is physically (i.e. passively) fail safe, while ground detection is an active safety measure? You can always put in two ground wires in the current system too... Is there some way for the ground wire to have a signal in it even if it were broken (via EMF)? Can the chip fail in an unsafe way?

nickff 2y ago
The system proposed in this piece could probably be safely implemented, but it would much more challenging to do than the author seems to indicate. There are a variety of failure modes that they ignore. The author also glosses over a 20% power loss (to heating), which would cost money and bulk to dissipate.
- wtallis 2y ago
  I particularly dislike how this article tries to sweep the power loss issue under the rug: The first mention of loss says that the isolation link is "responsible for about 50 percent of the charger’s power loss". The second mention of loss says "the power loss would be less than 20 percent". They want you to think that those numbers are comparable, and that they've reduced loss from 50% to 20%.
  - loeg 2y ago
    I can't really tell. They also claim this change would improve total energy efficiency by 2-3%. So maybe those numbers are supposed to be comparable.
  - DevelopingElk 2y ago
    The article needs absolute efficiency figures to know if this is a good idea. I also wonder if better conversation electronics could make a difference. I'm guessing there is some tradeoff between cost of conversion and volume/weight/efficiency. The other question is how this fits in with regenerative braking. Is this power conversion circuit dual purpose?
coryrc 2y ago
We also require arc-fault breakers in the electrical code for new construction despite even their first-order effects being negative. We're drowning in over-regulation and the most prominent people pretending to care aren't going after the real problems.
- tehjoker 2y ago
  Construction with decades old regulations and fast paced technology is a pretty different environment from electric vehicle development where regulators are (usually) actively trying to make things easier.
  - coryrc 2y ago
    Explain the bullshit CCS plug then. It's all protectionism and cronyism.
- jmb99 2y ago
  Arc-fault protections are required primarily due to lobbying by receptacle and panel manufactures, not because they provide a real benefit. The number of people injured due to arc faults is vanishingly low, and a better solution to the majority of applications is to replace the NEMA 5-15 receptacle with almost literally any other (or at least improve upon the design). A more fitting comparison might be ground-fault circuit protections, which do very much have real benefits in all required situations without any drawbacks, while being very cheap to implement (effectively, a current clamp driving a relay). On the other hand, feeding 7.2kV down a wire handled by very normal people in very normal (read: adverse; wet, humid, non-careful) conditions without any passive protections, relying on the portable (car) end to perform all of the shock safety is laughable at best. A bug in the car’s charging circuit (hardware, firmware, or software) and whoops, the chassis has 7200V to ground when the cable gets plugged in during a rainstorm. Engineering safety regulations and guidelines are written in blood. Anyone who doesn’t understand that is either ignorant of the dangers involved, or narcissistic to the point of believing they are immune to danger.
  - coryrc 2y ago

nickff 2y ago

The system proposed in this piece could probably be safely implemented, but it would much more challenging to do than the author seems to indicate. There are a variety of failure modes that they ignore. The author also glosses over a 20% power loss (to heating), which would cost money and bulk to dissipate.

wtallis 2y ago
I particularly dislike how this article tries to sweep the power loss issue under the rug: The first mention of loss says that the isolation link is "responsible for about 50 percent of the charger’s power loss". The second mention of loss says "the power loss would be less than 20 percent". They want you to think that those numbers are comparable, and that they've reduced loss from 50% to 20%.
- loeg 2y ago
  I can't really tell. They also claim this change would improve total energy efficiency by 2-3%. So maybe those numbers are supposed to be comparable.
- DevelopingElk 2y ago
  The article needs absolute efficiency figures to know if this is a good idea. I also wonder if better conversation electronics could make a difference. I'm guessing there is some tradeoff between cost of conversion and volume/weight/efficiency. The other question is how this fits in with regenerative braking. Is this power conversion circuit dual purpose?

coryrc 2y ago

We also require arc-fault breakers in the electrical code for new construction despite even their first-order effects being negative. We're drowning in over-regulation and the most prominent people pretending to care aren't going after the real problems.

tehjoker 2y ago
Construction with decades old regulations and fast paced technology is a pretty different environment from electric vehicle development where regulators are (usually) actively trying to make things easier.
- coryrc 2y ago
  Explain the bullshit CCS plug then. It's all protectionism and cronyism.
jmb99 2y ago
Arc-fault protections are required primarily due to lobbying by receptacle and panel manufactures, not because they provide a real benefit. The number of people injured due to arc faults is vanishingly low, and a better solution to the majority of applications is to replace the NEMA 5-15 receptacle with almost literally any other (or at least improve upon the design). A more fitting comparison might be ground-fault circuit protections, which do very much have real benefits in all required situations without any drawbacks, while being very cheap to implement (effectively, a current clamp driving a relay). On the other hand, feeding 7.2kV down a wire handled by very normal people in very normal (read: adverse; wet, humid, non-careful) conditions without any passive protections, relying on the portable (car) end to perform all of the shock safety is laughable at best. A bug in the car’s charging circuit (hardware, firmware, or software) and whoops, the chassis has 7200V to ground when the cable gets plugged in during a rainstorm. Engineering safety regulations and guidelines are written in blood. Anyone who doesn’t understand that is either ignorant of the dangers involved, or narcissistic to the point of believing they are immune to danger.
- coryrc 2y ago