Square AC servo motor

The utility model discloses a square AC servo motor capable of effectively guiding water in straight flutes of a casing. The square AC servo motor comprises the casing and a front and a rear end covers arranged at two ends of the casing, which are square in appearance and mutually matched via a waterproof port; a plurality of axial radiating ribs are arranged on the outer surface of the casing; and each straight flute is formed between two adjacent radiating ribs. The square AC servo motor is characterized in that a ring-shaped groove communicated with the straight flutes is formed on the inner side of at least one end cover, and is positioned at the bottom parts of the straight chutes; the water in the straight flutes of the casing flows into the groove on the at least one end cover from the end parts of the straight flutes; since the groove is circular, the water can flow into the lower part of the end cover from the upper part of the end cover and along the circular groove, then flow into the straight flut