General Speed-Torque Characteristics
Three-Phase Induction Motors
| NEMA Design | Locked Rotor Torque | Break- down Torque | Locked Rotor Current | % Slip | Relative Efficiency |
| B | 70-275%* | 175-300%* | 600-700% | .05-5% | Medium or High |
| Applications: Fans, blowers, centrifugal pumps and compressors, motor-generator sets, etc., where starting torque requirements are relatively low. | |||||
| C | 200-250%* | 190-225%* | 600-700% | 1-5% | Medium |
| Applications: Conveyors, crushers, stirring machines, agitators, reciprocating pumps and compressors, etc., where starting under load is required. | |||||
| D | 275% | 275% | 600-700% | 5-8% 8-13% 15-25% | Medium |
| Applications: High peak loads with or without flywheels, such as punch presses, shears, elevators, extractors, winches, hoists, oil-well pumping, and wire-drawing machines. | |||||
| E | 75-190%* | 160-200%* | 800-1000% | 0.5-3% | High |
| Applications: Fans, blowers, centrifugal pumps and compressors, motor-generator sets, etc., where starting torque requirements are relatively low. | |||||
Based on NEMA Standards MG 10, Table 2-1. NEMA Design A is a variation of Design B having higher locked-rotor current.
*Higher values are for motors having lower horsepower ratings.