NEMA MG 1-2011 Information Manual
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Condensed MG 1-2011Page 9© 2014 National Electrical Manufacturers Association8 DIMENSIONS—AC SMALL (FRACTIONAL) AND MEDIUM (INTEGRAL) MOTORS8.1 System for Designating FramesThe system for designating frames of motors consist of a series of numbers in combination with letters,defined as follows: [MG 1-4.2]8.1.1 Small MotorsThe frame number for small motors is the D dimension in inches multiplied by 16. The letters C, H, Y,and Z immediately follow the frame number to denote variations, for general purpose motors, as follows:[MG 1-4.2.2]C –Type C face-mountingH – Indicates a frame having an F dimension larger than that of the same frame without the suffixletter HY – Special mounting dimensions (dimensional diagram must be obtained from the manufacturer)Z – All mounting dimensions are standard except the shaft extensionNote: Other letters are also used to denote other motor types.8.1.2 Medium MotorsThe system for numbering the frames of medium motors is as follows, (see also Table 13, Figure 3,Figure 4, Figure 5, and Figure 6): [MG 1-4.2]a) The first two digits of the frame number are equal to four times the D dimension in inches. Whenthis product is not a whole number, the first two digits of the frame number is the next higherwhole number.b) The third and, when required, the fourth digit of the frame number is obtained from the value of 2Fin inches by referring to the columns headed 1 to 15, inclusive, in Table 13.The letters C, CH, D, R, S, T, U, V, Y, or Z immediately following the frame number are used to denotevariations as follows:C – Type C face mounting on drive end. (When the face mounting is at the end opposite the drive,the prefix F shall be used, making the suffix letters FC.)CH – Type C face-mounting dimensions are different from those for the frame designation having thesuffix letter C. The letters CH are to be considered as one suffix and shall not be separated.)D – Type D flange-mounting on drive end. (When the flange mounting is at the end opposite thedrive, the prefix F shall be used, making the suffix letters FD.)R – Drive end tapered shaft extension having dimensions in accordance with Table 21.S – Standard short shaft for direct connection (see Table 20, Table 21, Table 22, Table 23, andTable 24).T – Included as part of a frame designation for which standard dimensions have been established(see Table 20, Table 21, Table 22, Table 23, and Table 24).U – Previously used as part of a frame designation for which standard dimensions had beenestablished (no longer included in MG 1).V – Vertical mounting only.Y – Special mounting dimensions (dimensional diagram must be obtained from the manufacturer).Z – All mounting dimensions are standard except the shaft extension(s). Also used to designatemotor with double shaft extension. |
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