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General Speed-Torque Characteristics
Three-Phase Induction Motors

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.
Never Manufactured, Deleted from NEMA MG 1-2003.

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.

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