Electrical motor question

Factual Questions
1

What does the “frame” number mean on an electrical motor baseplate?

2

I couldn’t swear to it, but I believe it refers to the mounting form factor, i.e. where the bolt holes are located on the mounting plate.

FWIW,
Rob

3

Electric motor frame numbers explained.

4

Thank you.

5

Ahh! NEMA framesizes, where 149 is not followed by 150, but by 1410 and where a 48 frame might be a T48 or a U77*. (I never figured out whether the guys who dreamed up that scheme were simply ignorant of the possibility of computers, or whether they knew they were coming and wanted to play terrible mind games with unfortunate programmers.)

  • To be fair, the 48 frame example is from one company’s model number choices, not NEMA frames, but it was created by the same sort of twisted engineer’s mind.
6

While the numbering scheme seems largely arbitrary, it is truely wonderful the degree to which motors have been standardized. I’ve provoked wonder in many managers by picking up the phone, calling my local motor shop, or whoever, and while the replacement may be cosmetically quite different, it has never failed to bolt right into the spot from which the burned out motor was removed. The wonder comes from the fact that while the orgional machine that included the motor may have had a six week lead time, I can have it running again within 24 hrs usually.

7

I have no problem, at all, with the NEMA standards and I can handler framesize, phase, enclosure code and a host of other issues without any trouble. However, when some marketing guy wants me to create an analysis of sales by framesize and I have only a model number from which to extract and categorize it, I do tend to wish that NEMA had insisted on two separate fields for frame (or insisted on a two-digit shaft length) and that the people assigning model numbers (that require NEMA approval before they can be used) would pay just a bit of attention to how their numbers are laid out. Nothing in the NEMA schemes (aside from bad history and inertia) would have prevented a 169 frame from actually being designated 1609 or having some genuine rationale employed when assigning values to fractional motors.