1. Increasing the Percentage of Copper Windings
It is in the interest of higher efficiency to increase the cross-sectional area of copper windings in a motor. Motors experience losses related to this wire area and larger cross-sections always result in lower losses. Traditionally motor makers have “inserted” the windings into the long, narrow-opening slots, and thus have had difficulty in obtaining dense copper windings in the motor slots. The optimum solution is to wind the copper in a neat concentrated fashion onto each tooth, and subsequently build the motor around a series of these concentrated tooth windings. This concentrated approach is becoming more and more common as most motor makers are researc
hing or already employing this technique.
Related but not trivial is the reduction in end turn length. The end turns are the name given to the wire needed to “jump” the continuous wire from one slot to the next. In a concentrated winding, end turn length is minimized, compared to the long and looping end turns in the distributed winding. Long end turns are a source of waste heat as well as a wasteful use of expensive copper windings.
On the left, note the compact minimal windings, as opposed the long windings on the right. A negative of this approach is that the concentrated windings need low ratio of slots/phase/pole as discussed in section 3.