Lately, there is lot of random wound windings with no any phase to phase end windings insulation at motors coming out from rewind shops. Their explanation is that some of the original windings are made in that way very often and , also, they have no problems or complaints, even though for years they are doing so. Putting insulation in the end windings for them is a waste of time and money.
Our recommendaton:
This practice is justified in motors fed with very low voltage (less than 50V, except the VFD-driven motors). Also, sometimes the manufacturers apply such practices when they obtain conducors with extremely high-quality insulation and special impregnation method, which is usually not available to most service centers. In addition, what are the savings in time and material in this way? Probably they are negligible. New doubts may arise: what else they could do to reduce costs? Reduce the size of the conductor or the number of turns? Avoid the varnishing? ?? ......What else? What is our recommendation for rewind shops? There is no technical justification for doing so. Anyway, the savings are insignificant and the risk is too high. Do not do that way. You need to work the way you've learned during your professional training. What is our recommendation to owners of motors? Do not send your motors in such shops. Probably, there are other rewind shops that are working properly.