[TylerE]

Because you have to size the cables based on amperage. The highest voltage supported by USB-PD is 20V. At 20V to deliver 240W you need 12 amps. That's already a fairly high number. At 300W you'd need 15 amps.

So unless you want to drag around an NEC type cable as thick as one of your fingers, you need to set a limit.

Edit: Fixed math. I haven't had caffeine yet.

[kube-system]

That was my first question -- is this still going to be at 20V? The kind of current that would draw is crazy for those tiny pins.

Looks like the spec goes up to 48v now:

https://en.wikipedia.org/wiki/USB_hardware#USB_Power_Deliver...

[parineum]

It's 48V.

[ScottKolo]

While amperage is indeed a problem, PD 3.1 uses 48 volts to deliver 240W. https://www.usb.org/usb-charger-pd

That’s only 5 amps, but such a high-ish voltage is enough to lead to arcing. Charging cables are likely to require additional safety measures.

[delfinom]

Not even safety requirements, going above 48V will start subjecting to your device to electrical code.

[f_devd]

USB-PD now supports 28, 36V & 48V as well because of the higher wattage limit[0] (240/48=5A which is about what the cables are rated for I believe)

[0]: https://www.usb.org/usb-charger-pd

[edgineer]

The 240W profile uses 48V