Frame Size

This shows the frame size. The frame size determines the mounting dimensions such as the foot openings pattern and the shaft height.

The dimension of the electric motor based on the NEMA system for fractional hp motors (micro motors) have two digits and represent the shaft height from the base’s bottom in sixteenths of one inch.

For large motors the frame size has three digits, the first two digits stand for the shaft height in one quarter of an inch. The third digit is the bolt mounting holes dimension, the longer the motor body, the longer the distance between mounting bolt holes in the base. Finally, the letter is the type of frame.

The same concept applies for IEC type motors (metric motors) but the height is measured in millimeters instead of inches.