How to improve motor efficiency?

I have been in the electric motor repair industry for 50 years. Over the years we have gone from rewinding everything in site to 50-hp motors being uneconomical to repair. This meant that the electric motor service companies entered the replacement motor market. Over the years the market has become extremely competitive with the end user looking for the cheapest motors around. Nobody in the electric motor business will tell you it is not competitive. Let's be honest. "T" FRAME MOTORS WITH COPPER BARRED ROTORS AND MAGNETIC WEDGES?". Have you seen the inside of today's "T" frame motor. It is very basic. The cost would sky-rocket and with a fraction of a percentage point improvement in the efficiency. the life of the motor would not be improved.

Efficiency is built into a motor on design and on the quality of the steel that makes up the laminated core. The fan and bearings are also a factor. "T" frame motors have quite a heavy slot fill so there is not much you can do with conductor size. There is not a lot you can do with bearings because the housings and journals are manufactured for a specific bearing series and size. You could put a smaller fan but the motor would overheat. In a rewind situation you have to be extremely careful to maintain the efficiency. Trying to improve it is futile. Large motors are normally quite efficient, even the older once are not terribly inefficient, it is the smaller motors that are the biggest offenders and if the best efficiency available is required, "Buy a New One".

Magnetic wedges are normally found on medium voltage machines and offer little in efficiency improvement. I see the repair industry is getting a bad rap again.
Magnetic wedges are not very strong and the function of a wedge is to ensure that the coil is properly bottomed and that movement is mainly eliminated. A slot wedge, no matter what the construction, should be an easy fit in an empty slot and tight when it is being put on top of a coil. if packing is required to make it tight it is placed under the wedge. this way you know that the wedge is pushing the coil down. Magnetic wedges have a tendency to come apart when being knocked into a properly packed slot. Maybe the rewind shops try to too hard to properly bottom the coil.

The repair industry is very often under the gun to deliver the motor. Magnetic wedges are not readily available and customers are not willing to wait. I have yet to receive an end-user complaint when magnetic wedges are replaced with the stronger fiber wedges.