Different motors of the same rated horsepower may have different starting currents, torque curves, speeds and other variables. NEMA (National Electrical Manufacturers Association) has A, B, C, D four different designs for electric motors.
NEMA Design B: Is the most common design of electrical motors and ATO single phase AC induction motors are of NEMA design B. Its starting torque is similar to that of design A, but sometimes still lower, providing a relatively low starting current. However, in industrial application, it locks locked rotor and still allows starting load. The rotating-speed difference is lower than or equivalent to 5%. The electric efficiency and full-load power factor are relatively high. The typical applications include pump, fan and machine tool.