[Daox]

The main reason these motors are smaller is because they have an open frame design for cooling. This means less heat build up so you can pack more power in a smaller package.

Motor rating is mostly about heat dissipation. You can run a 1hp series wound motor at 50 hp for a split second. If nothing melts and you don't ruin the bearings you're good to go. That is why my 1.2 hp motor could put out 5 hp for half hour spurts for a year and a half.

The other advantage of the permanent magnet motors is they keep a more constant rpm as I mentioned in my first post. Its not that a series wound motor is bad, it just changes rpm more based on the load put on it. Series wound have other advantages though, but they don't really apply much to a mower type setup.

Now, I think I've seen both series wound and permanent magnet motors used in forklifts as pump motors. I think the easiest way to identify a series wound motor is that it normally has 4 posts on it versus 2 posts for wires.