Eh, they do raise a valid point: Disconnecting voltage from a coil (which could be a motor winding or could be anything else inductive) generates back-EMF. It has to.
If there was a motor running (aircon, furnace blower, clothes dryer, whatever) when the main breaker tripped, then: Back-EMF is very likely to be a thing.
It's a simple thing, and it's how spark plug coils on car engines still work today: Send (boring 12VDC in this case) power to a coil, and take it away rapidly. This essentially angers the coil and makes produce a high voltage: High enough to jump the gap of the spark plug. The voltage maximum will be higher as the spark gap is increased, and lower as it is decreased.
And in the author's case, that back-EMF voltage will be sent to all of the household wiring. That's obvious on single-phase systems like Europe mostly has, and here it would also be the case even on split-phase systems like in North America (I don't know where the author was located), wherein: The electric range was reportedly faulted short, bridging the two hot legs together.
However, a modern household's electrical system is full of all kinds of stuff that is trying to use electricity. It presents a fairly low impedance. Things with linear power supplies (rectifiers and capacitors) will work to soak up any rise in voltage. The increasingly-common switch-mode power supplies that modern homes are full of tend to have MOVs on their mains input, as is also the tendency for even dollar-store power strips that modern homes tend to be littered with. (PC power supplies are also protected with MOVs.)
And the lower the impedance, the lower the voltage maximum of the back-EMF spike. It's got almost zero current behind it, and Ohm's law didn't just drop out of existence when the main breaker tripped.
This has the net combined effect of tending to reduce the back-EMF voltage from the ZOMG! level that it could be on an isolated test bench, to a complete non-issue status in a real household.
Our motor loads at home are not usually very beefy, and we've got MOVs (and power supplies with caps, including LED bulbs) scattered all over the place, and that all conspires to snub the back-EMF.
---
So what happened, then?
I think it's just a case of false causation here on HNN. The author is rightly proud of his nearly four-nines uptime, which is pretty cool -- but it also means that the hard drive had been spinnamathingin' nearly continuously for as long as 14 years.
An old hard drive that dies after a sudden power drop seems more likely to be caused by age, than by back-EMF smoking only that particular computer component and leaving everything else in the house unscathed.
All of us here have probably had hard drives die (this is how we learn about backups!), including hard drives that were working seemingly-fine yesterday and that did not work after turning the computer off (and back on again) today.
That is very normal and expected behavior for hard drives, which have always shared the common trait that all of them must die eventually.
There's nothing to see here. There is no smoke, and no mirrors, and no-one is behind the curtain.
If there was a motor running (aircon, furnace blower, clothes dryer, whatever) when the main breaker tripped, then: Back-EMF is very likely to be a thing.
It's a simple thing, and it's how spark plug coils on car engines still work today: Send (boring 12VDC in this case) power to a coil, and take it away rapidly. This essentially angers the coil and makes produce a high voltage: High enough to jump the gap of the spark plug. The voltage maximum will be higher as the spark gap is increased, and lower as it is decreased.
And in the author's case, that back-EMF voltage will be sent to all of the household wiring. That's obvious on single-phase systems like Europe mostly has, and here it would also be the case even on split-phase systems like in North America (I don't know where the author was located), wherein: The electric range was reportedly faulted short, bridging the two hot legs together.
However, a modern household's electrical system is full of all kinds of stuff that is trying to use electricity. It presents a fairly low impedance. Things with linear power supplies (rectifiers and capacitors) will work to soak up any rise in voltage. The increasingly-common switch-mode power supplies that modern homes are full of tend to have MOVs on their mains input, as is also the tendency for even dollar-store power strips that modern homes tend to be littered with. (PC power supplies are also protected with MOVs.)
And the lower the impedance, the lower the voltage maximum of the back-EMF spike. It's got almost zero current behind it, and Ohm's law didn't just drop out of existence when the main breaker tripped.
This has the net combined effect of tending to reduce the back-EMF voltage from the ZOMG! level that it could be on an isolated test bench, to a complete non-issue status in a real household.
Our motor loads at home are not usually very beefy, and we've got MOVs (and power supplies with caps, including LED bulbs) scattered all over the place, and that all conspires to snub the back-EMF.
---
So what happened, then?
I think it's just a case of false causation here on HNN. The author is rightly proud of his nearly four-nines uptime, which is pretty cool -- but it also means that the hard drive had been spinnamathingin' nearly continuously for as long as 14 years.
An old hard drive that dies after a sudden power drop seems more likely to be caused by age, than by back-EMF smoking only that particular computer component and leaving everything else in the house unscathed.
All of us here have probably had hard drives die (this is how we learn about backups!), including hard drives that were working seemingly-fine yesterday and that did not work after turning the computer off (and back on again) today.
That is very normal and expected behavior for hard drives, which have always shared the common trait that all of them must die eventually.
There's nothing to see here. There is no smoke, and no mirrors, and no-one is behind the curtain.
Hard drives die.