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Comment by amluto | Hacker News Reader

How many residential devices actually ought to contain a three-phase motor running at fixed frequency? (And I mean now, in 2023, not in 1990.)

I can think of three, sort of:

1. A well pump, pumping from a high-producing well, into a tank or pond at the surface, where the pump is sized to efficiently pump somewhat less than the well’s production.

2. A pool or pond pump which, by some miracle, has been correctly sized for the system, and which, by some other miracle, is more appropriate in the application in question than an Intelliflo VSF or similar pump.

3. HVAC fans. But these are usually pretty small, and better systems usually use ECM motors.

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There are tons of people who have garages with table saws, air compressors, etc. that would benefit from 3 phase power.

I think that's overselling. I mean, sure, 3 phase is better for motors and you can get more power a little more efficiently and with less vibration to deal with in the mechanical design. And that's valuable. But come on, US workshop afficionados are doing just fine. No one is crying in their shop wishing for the blissful experience of a Danish band saw or whatever. It's better. It's not that much better.

What actually wins this fight is on the other side. A two-connector polarized NEMA 1-15 plug is a tiny, convenient, easy to use form factor that will still deliver 1400W. The experience of a normal consumer plugging in their normal junk in the US is just plain superior to the poor folks across the oceans charging their devices with BS1363 connectors that are almost bigger than the phones. And don't even get me started on Europlug.

Every time I try to charge something from a US socket the charger cable will frequently fall out of the socket due to poor design tolerances. Never an issue with EU sockets.

Sadly most outlets in the USA are installed by builders who buy these cheapest pieces of crap they can find.

Spend $5 or more an outlet and the plugs will work quite well.

(These kinds of things are what you should focus on if you build - materials are relatively small compared to labor and doubling your material cost on things like outlets can make a much nicer house. And if you want a UK outlet, you could get one wired up.)

BS1363 plugs are joyfully oversized, yes (and make excellent caltrops if dropped) but they are in other ways excellently engineered. Inherently polarised, fuses to protect the appliance wiring[0], socket shutters that open on the earth pin only to prevent vigorous insertion of metal by children, sleeved conductors to avoid shock when partially inserted, essentially unbendable...

Plus, I will fight anyone who suggests that 1400W is enough for a decent kettle ;-)

[0] Admittedly this was mostly included to offset the idiosyncrasies of final ring circuit wiring, but it's still better than just a big breaker.

BS1363 are comically oversized because they contain internal fuses, due in part to the strange ring main design, itself a vestige of WWII copper shortages.

I have all three of these and absolutely none of them contain (or will contain at any point) a three phase motor. All three of these use variable speed motors in my house. I suspect even more will moving forward as well. So honestly three phase is pointless as I just need "power" to drive the variable speed controller system. My hottub has fixed speed 220 pumps but its old. I suspect newer systems would be moving to variable speed as well.

I think your pretty spot on that most people do not need 3 phase, even in the limited cases you mentioned. =)

If you have a variable speed well pump, it is very likely to contain a three-phase motor. What it doesn’t have is direct wiring from the motor windings to incoming power. It likely has a variable-frequency drive consisting of an AC/DC converter (for which there would be a small but nonzero benefit if the supply were three-phase supply) and three inverter outputs connected to the windings. And hopefully either the VFD is in or very close to the motor (Grundfos will sell you a VFD/motor/pump combo like this) or has proper filtering to reduce high harmonics and properly shielded wiring to the motor.

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