I just bought a 110 amp 220v arc welder, does this mean I need a 110+
amp circuit breaker?
If you are in England that would be 230 volts, 50 Hz. However, if
you are in North America, then it is 240 volts, 60 Hz.
The 110 amps will be the secondary current. The primary side
current will likely be 1/4 of that or around 30 amps max. If it is
a fairly recent welder it should have a capacitor inside to correct
the phase angle somewhat, which helps to minimise the current draw
at max amps.