This air cooler is applied to cooling circular high-temperature gas(air or hydrogen) resulted from thermal losses in the operation of generator. Its design pressure is no more than 4.0 Mpa(marine) or 1.0 Mpa(land) on water side, design temperature of cooling water inlet is no more than 32℃(marine) or 40℃(land), design pressure on air side is no more than 0.05 Mpa and inlet design temperature is no more than 120℃. Its cooling medium is water and cooled medium is circular gas in winding of electric generator. Its practical working parameter is subject to the technical agreement or order.