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NEMA Nameplate Standards

Posted by WE Electric Motors on 4/9/2015

In order to follow NEMA standards, motor nameplates must include 12 specific items. These items include:

  1. Manufacturer’s type

  2. Rated volts and full load amps

  3. Rated frequency and number of phases

  4. Rated full load speed

  5. Rated temperature rise or the insulation system class

  6. Time rating

  7. Rated horsepower

  8. Locked rotor indicating code letter

  9. Service factor

  10. Efficiency

  11. Frame Size

  12. Design Code

Additional information may also be included on a nameplate, but is not required by NEMA standards.

  1. Manufacturer’s type

    1. definition varies from manufacturer to manufacturer (no industry standard), however, it is often used to define 1 or 3-phase, single or multi-speed, construction. Some of the types of motors you may come across when looking at “type” are:

      1. 1-Phase, Shaded Pole- low cost, low starting torque, low efficiency, no capacitors

      2. 1-Phase, PSC (Permanent Split Capacitor)

      3. 1-Phase, Split Phase

      4. 1-Phase, Capacitor-Start

      5. 3-Phase

      6. AC/DC (Universal or Series wound)

      7. Shunt Wound and Permanent Magnet DC

      8. General Purpose Motors

      9. Special Purpose Motors

     2.   Rated Volts

  1. voltage at which the motor is designed to operate and yield optimal performance

     3.   Full Load Amps (FLA)

  1. when the full-load torque and horsepower is reached, FLA is the corresponding amperage


     4.  Rated Frequency

  1. frequency the motor is designed to operate and is represented by Hertz (Hz)

     5.  Number of Phases

  1. number of AC power lines supplying the motor (single or 3-phase)

     6.  Full Load RPM

  1. approx. speed under full-load conditions, when voltage and frequency are at the rated values, generally listed as “RPM” on the nameplate

     7.  Synchronous Speed

  1. the theoretical speed of a motor based on the rotating magnetic field

     8.  Insulation Class

  1. thermal tolerance of the motor winding

     9.  Maximum Ambient Temperature

  1. point at which the motor can operate and still be within the tolerance of the insulation class at the maximum temperature rise, often listed as “AMB” on the nameplate

    10.  Altitude

  1. the maximum height above sea level at which the motor will remain within its design temperature rise

    11.  Time Rating

  1. the length of time the motor can operate at its rated load safely, also indicates if the motor is rated for continuous duty; shown as “CONT” on the nameplate

    12.  Horsepower

  1. a measure of the motor’s mechanical output rating, its ability to deliver the torque required for the load at rated speed