I have a air compressor which on the plate states 230 - 240v / 50hrz / 8amp and I believe it has a 1.75hp motor. I want to run this off a petrol generator, what size generator do I need in Kv (ie 1 Kv 2.5Kv 8Kv etc etc.) Thanks Barry

I would say at least a 2.2kw genny.

240V x 8A = 1920W, so a 2KW generator will be running near to it's limit. (KV is kilovolts, KW is kilowatts. Power is measured in watts...)

I'd suggest a 3 to 4KW generator to be on the safe side.

As a secondary check, 1hp is approx 750W, so a 1.75hp motor consumes about 1.3KW. I'd still go for 3KW or more though!

Ed.

Its not the steady state running that is an issue running a compressor off a genny, more the initially pull to kick it into action. Even quite small compressors need a good lump of power from a genny to get them running!

240 x 8amps = 1940 va, then you need to take account of power factor which will be about 0.8

so 1940/0.8 = 2425 watts

then you need to take account of starting current.