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Experience: Repair motor or Rewind motor

I have been in the electric motor repair industry all my working life, (50 years) and I have watched this industry progress. During my apprenticeship in the UK we were taught all about the damages that can be done to a stator core if proper procedures were not followed and in all honesty when I first arrived on Canadian shores I was horrified at some of the methods. Much has changed since them although there are still some shops that throw the motor into a fire and reduce the size of conductor to make a high efficiency motor easier to rewind. In these days it was only medium and high voltage cores that were tested for losses. Nowadays all cores are tested for losses.
In many ways the high Efficiency Motor Program promoted by "Ontario Hydro" did much to bring the importance of correct procedures to the industry. Up until then many had never seen a core tester. Yes they did do an experiment wither they had several different shops, rewind identical 40-hp motors and yes they did find an efficiency decrease in, (if my memory serves me correctly) in 2 out of seven motors. The shops were never identified but it served to inform the electric motor user that your choice of rewind facility should not be taken lightly. It also served to inform some facilities that they were not following proper procedures.
We use a class "F" insulation system because our practices cause excessive heat in the core. Not so, I think it might be time to stop tarring the many with the same brush as the few. The manufacturer almost exclusively uses class "F and nameplates a class "B" rise. It is our job to match our better the manufacturers quality.
As I said above, I have been in the electric motor repair industry for 50 years and I have always followed the progress in materials and equipment. I saw my first burn off oven in 1965. Our industry provides a quality service all over the world not only informing the customer that their motor needs to be rewound but also in telling them "when it SHOULD NOT BE REWOUND."
I probably don't have a lot of years left in this industry but my time in it has been very rewarding and if I did not think that our industry provides quality and service i would have left it a long time ago.

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