Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications! NEMA has established the four different designs A, B, C and D for electrical induction motors.
Different motors with the same nominal horsepower may have different start current, torque curves, speeds and other variables. When selection a particular motor for an intended task all engineering parameters must be taken into account.
NEMA (National Electrical Manufacturers Association) designs have unique speed-torque-slip relationships - making them suited for different type of applications. NEMA design A maximum 5% slip high to medium starting current normal locked rotor torque normal breakdown torque suited for a broad variety of applications - like fans and pumps NEMA design B maximum 5% slip low starting current high locked rotor torque normal breakdown torque suited for a broad variety of applications with normal starting torques - common in HVAC application with fans, blowers and pumps NEMA design C maximum 5% slip low starting current high locked rotor torque normal breakdown torque suited for equipment with high inertia and high starting torques at start - like positive displacement pumps, conveyors NEMA design D maximum 5-13% slip low starting current very high locked rotor torque suited for equipment with very high inertia starts - like cranes, hoists etc. Related Topics Electrical units, amps and electrical wiring, wire gauge and AWG, electrical formulas and motors. Related Documents Calculate electric motor efficiency. IEC and NEMA torque classifications of electrical motors. Slip is the difference between an electrical induction motor's synchronous and asynchronous speed. Full load operating torque vs. break down, pull up and locked rotor torque. Electrical motors NEMA frame dimensions. NEMA frame assignments. NEMA - electrical motor efficiency ratings. National Electrical Manufacturers Association. Full load amps, wire and conduit sizes for three phase electrical motors.
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