What amp supply would power a 240 volt air compressor?

Read the label on the air compressor or its User Manual. Find what power it takes in Watts and divide the power by the Voltage (240 volts in this case.) The result is the basic current drawn in amps. But that is not enough information to decide what size circuit breakers and wiring should be installed. The answer will depend on length of cable run required from breaker panel to wall outlet and the Wiring Codes or Regulations for your locality. (Town/State.) If you don't know how to calculate these, call a licensed electrican to advise you or do job for you. IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB

SAFELY AND COMPETENTLY

REFER THIS WORK TO QUALIFIED PROFESSIONALS. If you do this work yourself, always turn off the power at the breaker box/fuse panel BEFORE you attempt to do any work AND always use a meter or voltage indicator

to insure the circuit is, in fact, de-energized.