NEMA SM 1:2017

This guide covers general-purpose synchronous motors without excited rotor windings, including polyphase alternating-current permanent magnet motors rated 500 horsepower and less, designed in standard ratings with standard operating characteristics and mechanical construction for use under usual service conditions without restriction to a particular application or type of application, and incorporating all of the following: a. Across the line starting b. Permanent magnets in the rotor c. Open or enclosed construction d. Rated continuous duty e. Class B or higher rated insulation system with a temperature rise at rated load not exceeding that specified in 7.15 for Class B insulation.