Below is a list of 1/2 HP Motor manufacturers from St. Louis, Missouri. ½ horsepower (HP) motors are fractional horsepower motors with a power output of ½ HP, which is roughly equivalent to 373 Watts. A motor is categorized as a fractional horsepower motor if the power output is less then 1 HP, but also if the power output exceeds one HP while the frame size fits within the dimensions of 42, 48, 56. These categorizations are standardized by the National Electrical Manufacturers Association (NEMA) standards.