I just bought a new Arc welder (input capacity 15.2 KVA, 35% duty cycle). I will splice into the overhead power lines coming into the building and install a separate breaker and plug for the unit about a 10 meter run to the new breaker. My calculations indicate that the wire size should be 16MM2 copper, but the manual indicates 10MM2 copper is acceptable. Which is correct? If 10MM2 copper is okay I shpould be able to get away with 16MM2 aluminum which I already have and could save some money!

10mm² Cu will be fine on a current rating basis taking into account the duty cycle, volt drop over 15m will be about 2%

16mm² Al will be fine.

I'm assuming the welder and supply is single-phase, what size meter do you have?

Thanks. Meter size is 15/45. I have another welder, heavy and not portable, hooked up to it in another building with no problems. That one is installed using 25MM2AL that I had leftover when I built the house.. I'll never use both at the same time.

Only added suggestion i can make if you want to transport the welding machine from its place adding length to the supply wire....be sure NOT to coil the feeding ac wires..........causing spool effect and overheating supply lines!!