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ELECTRIC MOTOR (NFPA 20 Chapter 9)

Induction motors – also known as asynchronous motors – are the most common type of electric motor used today. Due to their simple design, low cost, and high reliability, induction motors are used for a wide range of applications in all engineering industries.


LISTING & SELECTION:

9.5.1.1 All motors shall comply with NEMA MG-1, Motors and Generators, and shall be marked as complying with NEMA Design B standards for three-phase motors


3.3.58 Service Factor. A multiplier of an ac motor that, when applied to the rated horsepower, indicates a permissible horsepower loading that can be carried at the rated voltage, frequency, and temperature. For example, the multiplier 1.15 indicates that the motor is permitted to be overloaded to 1.15 times the rated horsepower.


9.5.2.2 The following shall apply to the service factor:

(1) The maximum service factor at which a motor shall be used is 1.15.


9.5.2.4 General-purpose (open and dripproof) motors, totally enclosed fan-cooled (TEFC) motors, and totally enclosed nonventilated (TENV) motors shall not have a service factor larger than 1.15.