NEMA Frame Sizes: A Guide to Motor Mounting and Dimensions
When replacing or selecting an electric motor, it's not just about horsepower or voltage—the NEMA frame size is critical. It defines the motor’s mounting footprint, shaft height, and overall dimensions. If you choose the wrong frame, your motor won’t fit, even if the specs match.
RECOMMENDED: Use our NEMA Frame Finder Tool to find what you’re looking for.
This guide explains what NEMA frame sizes mean, how to read them, and provides a handy reference chart for ABB motors and other NEMA-compliant equipment.
What Is a NEMA Frame Size?
The NEMA frame size is a standardized code established by the National Electrical Manufacturers Association (NEMA). It represents the physical dimensions of a motor, not its electrical performance.
The frame number tells you:
Bolt-hole spacing
Shaft height from base
Flange size (if applicable)
Overall length and width
Why Frame Size Matters
Selecting the correct frame size ensures:
Mounting compatibility with existing equipment
Shaft alignment with driven machinery
No surprises during installation
Standardization across brands like ABB, Baldor, Leeson, etc.
Understanding Frame Size Code
Most frame size codes consist of three or four characters:
Digits (e.g., 56, 143T, 256TC): Shaft height and mounting dimensions
Suffix letters (e.g., T, TC, TD): Indicate features like C-face flange or D-flange mounting
For example:
56C = Standard small frame with C-face mount
145T = Standard shaft height, T-frame
184TC = T-frame with C-face and standard mounting holes
NEMA Frame Size Chart (Quick Reference)
| Frame Size | Shaft Height (in) | Mounting Hole Spacing (in) | Notes |
|---|---|---|---|
| 56 | 3.5 | 3 x 5 | Common for fractional HP motors |
| 143T | 3.5 | 3 x 5 | T-frame motors |
| 145TC | 3.5 | 3 x 5 | C-face mount, footed |
| 182T | 4.5 | 5 x 6.5 | Standard industrial motors |
| 184TC | 4.5 | 5 x 6.5 | C-face, rigid base |
| 256T | 6.5 | 7.5 x 9.5 | Higher HP motors |
Mounting Styles and Variations
C-Face – Flat face with bolt holes around the shaft for direct coupling
D-Flange – Rear-mounted flange for vertical or horizontal installations
Rigid Base – Traditional foot-mounting
Resilient Base – Shock-absorbing for vibration-sensitive installs
ABB Motors and NEMA Frame Compatibility
ABB motors follow full NEMA standards, meaning their frame sizes, shaft heights, and mounting bases match across all U.S.-standard motor applications. Whether you’re replacing a Baldor, Leeson, or WEG, you can easily cross-reference the frame size and swap in an ABB motor.
Need Help Selecting the Right Frame?
Whether you're replacing an existing unit or designing new equipment, Industrial Gearbox Supply can help match the correct NEMA frame size with the horsepower, speed, and enclosure you need.
Contact us today:
Phone: (517) 858-2966
Email: sales@industrialgearboxsupply.com
Website: industrialgearboxsupply.com
Location: 3590 Scheele Dr, Jackson, MI 49202