Abstract: Electrical machines comprising a rotatable armature and permanent magnets surrounding and separated from the armature by air gaps having a length to width ratio not greater than 60:1 and a minimum width of 0.040 inch irrespective of the length to width ratio, thereby allowing cooling air to be circulated through the air gaps as well as through the annular gaps between the magnets. Such machines have a substantially higher steady state power output than permanent magnet machines of the same overall dimensions designed in accord with conventional techniques because of materially improved armature cooling.