Thickness of Laminations

Take it apart and measure one, or ask the manufacturer.

Sounds pretty complicated. Have a read of this:-

http://link.springer.com/article/10.1007%2Fs00202-012-0237-7#page-1

(After you paid for it) or find similar articles.

p.s. good luck with the DC version.

I have seen several good white papers put out by, I believe, the EPRI (Electrical Power Research Institute) on design considerations for improving motor efficiency that included discussion of lamination design as well as steel quality used to lower the eddy current losses. If it wasn't the EPRI, then it was the US Department of Energy, in what was once called their "Energy Matters" program for improving electrical efficiency. You will have to search on your own however.

JRaef (the Lumberjack): Out of curiosity, and never worked this industry of AC machines, is the laminate thickness controlled by the accuracy detail of the stacked up laminations? I'm of the belief that thick material would have more difficulty in holding fine punch pressed detail, as well the wear on the dies of too thick a stamping material. From memory they call this silicon steel, which probably is much tougher then low carbon mild hot rolled relative to punch die life.

So there must be a trade off of laminate thickness vs tool life vs # of laminates vs allowable eddy current vs core required tolerance.

Find an area where you can measure the thickness of the core, count the number of laminations and divide. The lamination thickness includes the insulation, but that is very thin and usually just a controlled oxide on the surface. Transformers can be 8-14 mills and motors are usually a max of 25 mils. The thinner the better, since it cuts down eddy loss in the steel. The thicker they are the more energy you pay for as you use the device and core loss is there even if the load is small.

Not only thickness but material used too play a role in losses.

Why you want to measure the thickness of lamination ? If it for replacing the faulty of damaged portion of the core (in most of the cases this is done best by the manufacturer of the original equipment supplier) then you need to know not only the thickness bot also the grade of the still. Generally the manufacturer specifies the grade and thickness of the steel used in their documents (Operating manual). Otherwise as suggested in other reply, measure the length of core packet and count the number of lamination. The measured length would be gross length and the net iron length can be arrived at by assuming stacking factor of 0.9 to 0.95. Generally this standard thicknesses are 0.35 mm, 0.5 mm, 0.65 mm and 1 mm. Varnish thickness may be of the order of 6 to 8 microns on each side of the lamination.

If you are trying to decrease the back EMF why don't you try what we did around 1990. We were racing slot cars and got a manufacturer to lace aluminum laminations within the stacks it helped quite a bit, also helped cut down on the heat in the armature. And it also cut back on the weight, as well as increased the RPM. The only loss was in torque but not enough to go back to all steel laminations. Most of the laminations we used were 5-7 thousandths