NEMA Frame/Shaft Sizes
Frame numbers are not intended to indicate electrical characteristics such as horsepower. However, as a frame number becomes higher so in general does the physical size of the motor and the horsepower. There are many motors of the same horsepower built in different frames. NEMA (National Electrical Manufacturers Association) frame size refers to mounting only and has no direct bearing on the motor body diameter.
By NEMA definition, two-digit frame numbers are fractional frames even though 1 HP or larger motors may be built in them. Three-digit frame numbers are by definition integral frames. The third numeral indicates the distance between the holes parallel to the base. It has no significance in a footless motor. Refer to NEMA Standard Dimension Chart.
NEMA Suffixes
| C | = | NEMA C face mounting (specify with or without rigid base) |
| D | = | NEMA D flange mounting (specify with or without rigid base) |
| H | = | Indicates a frame with rigid base having an F dimension larger than that of the same frame without the suffix H. For example, combination of 56H base motors have mounting holes for NEMA 56 and NEMA 143-5T and a standard NEMA 56 shaft. |
| J | = | NEMA C face, threaded shaft pump motor |
| JM | = | Close-coupled pump motor with specific dimensions and bearings |
| JP | = | Closed-coupled pump motor with specific dimensions and bearings |
| M | = | 6 3/4" flange (oil burner) |
| N | = | 7 1/4" flange (oil burner) |
| T, TS | = | Integral horsepower NEMA standard shaft dimensions if no additional letters follow the "T" or "TS." |
| TS | = | Motor with NEMA standard "short shaft" for belt driven loads |
| Y | = | Non-NEMA standard mount; a drawing is required to be sure of dimensions. Can indicate a special base, face or flange. |
| Z | = | Non-NEMA standard shaft; a drawing is required to be sure of dimensions. |
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Types of Enclosures
Mounting
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