You could geek out and learn the difference of upstream (A, host) and downstream (B, device) ports, the various types of B port sizes, and that was it. Later USB 2.0 was introduced and just (bam!) made it all 40 times faster, but it still logically worked pretty much the same.
Then USB 3.x came and just blew all that to h-ll, which is frustrating for both old bearded geeks, and* new/non-technical users.
Except that my desk has three USB cords, each with a color-coded label so that I can tell what each one is for. One is seemingly the only one that will charge my e-reader, but only does low speed data transmission so it never really gets used for anything but my e-reader. Another is power only and therefore useful for charging devices without my computer attempting to talk to them. And a third is a proper, modern (ish, I suppose), well-behaved USB 2.0 cable.
You do see NEMA 5-15R receptacles on 20A circuits in residential applications, but that's probably because most appliances don't require 20 amps. A 5-15 connector has two vertical prongs, a 5-20 has a horizontal and a vertical, with the special case of receptacles with a T slot that fits both 5-15 and 5-20 plugs.
It goes a bit deeper than that though: A NEMA 6-20 also has a horizontal and vertical prong, but they're reversed from a 5-20 so you can't plug them in in an incompatible (and likely hazardous) way.
The whole standard is really well thought out. I went down the rabbit hole when I got an old table saw with a 6-20 plug and had to figure out what the hell to plug it in to (dryer outlet, via a "custom" extension cord).
I feel like I haven't seen too many uses of Schrader valves that are likely to cause havoc. Most of the use cases for them besides tires are pretty obviously special and distinct from one another. I mean, I'd hope nobody's ever hooked a bike pump up to their air conditioner or a can of R134a to a tire...
This is, of course, what I was talking about. I do appreciate the nuances of the 15/20 T-socket and the 6-20/5-20 symmetry; NEMA is super cool (aside from the fact that bladed plugs that aren't twist-lock are sort of lame/less safe in general, at least compared to the UK standard bladed plug). It's a fun rabbit hole to venture down: my occasion was having to adapt straight-blade wall box receptacles that the electrician installed to the twist-lock of the PDUs we had bought.
There's also a fun and confusing mess of competing DC connector standards. I haven't decided what 12/48VDC connectors I'm going to put into my new house build yet (beyond the obviously mandatory 5V USB).
Stupid question: are there any common household appliances that draw 20A? I've only ever seen the T receptacles in non-household uses.
FWIW if the nameplate of the motor specifies current draw at 120V, you can likely reconfigure the motor to use 120V instead of 240V.
[0] take a look at the gauge of a dryer's internal wiring, which is regulated by UL/CE and not NEC.
Rewiring the motor to 115v is probably a no-go, since it's a 3hp motor (continuous), which I believe is more amps at 120v than could be drawn from a normal circuit.
For safety, I'm wondering what kind of faults wouldn't be protected against. The starter has built-in thermal protection (heaters), which should protect the motor from the unlikely use case where I'm pushing the saw too hard, or more likely, a stall on start-up.
The breaker should still protect against shorts. I'm not knowledgeable enough to know what other faults could lead to an over current fault that one or the other of those wouldn't catch.
Would anybody care to educate me?
Also: the most dangerous aspect of a table saw is probably not the potential for electrical faults :-)
I'm having a hard time coming up with a compelling failure mode, given that thermal protector. Perhaps when the rotor locks, the thermal protector has a slower curve than the saw's wiring (which is assumed to be protected by the circuit breaker's curve). I would hope the saw wiring would be a bit oversized such that it too was protected by the motor thermal protection, but without doing an engineering analysis of the saw itself, you don't really know.
Unknown unknowns are my real point though - you're operating outside of the electrical code. Same as if you wired up a workbench of 5-15 receptacles with 10ga and put a 30A breaker on it - realistically it's going to be fine, but we avoid doing this. All those different NEMA plug sizes exist for a reason. 5-15/5-20 is really an anomaly where you can plug the smaller into the bigger, and even there I've got to wonder if eg old table lamps on a nice stiff 20A circuit are a good idea, or if they just haven't been focused on because they're statistically unimportant (see also: strings of Christmas lights with receptacles at the end).
FWIW I'd probably do the same thing you did, but at the cost of making sure I unplugged the saw whenever I was done using it until I made a proper permanent circuit. But that is not professional advice!
Before: "Here in the back of the computer we have PS/2 ports (1 for keyboard and 1 for mouse), a parallel port, serial, 25-pin serial, game port".
Introducing USB: "Everything is USB now! Plug anything anywhere!"
USB version whatever: "Well the sockets look all the same, but you can only plug your display in here, to charge it you have to connect it here", etc, etc.
With USB-A and -B, there is a physical indication of the direction of flow (data and/or current). Just "connecting" two things is sometimes unambiguous, but sometimes it's not.
You mean that one can hold 15A and the other - 20A? If so, they do work the same, they just have different capacities (like a tap, some of them will provide more water, others less but they work the same (especially if they look the same))