The “bonding of the windings” by Joule heating is performed in order to eliminate impregnation with paints or resins and to block and better insulate the windings of small-medium stators of electric motors, with considerable savings in terms of costs and time.
Indeed, the bonding of the windings relies on the use of enameled wires coated with an additional layer of thermosetting paint which softens when heated. Thus allowing bonding with the adjacent wires, and polymerizes when the required temperature is reached, therefore stabilizing the process.
This operation allows considerable savings, in terms of
- material (paints or resins)
- equipment (ovens and impregnation tanks)
- energy (since only the copper wire is heated, rather than the entire stator and the air for heating)
- time, since the operation takes only a few seconds: 15 – 30” (compared to a few hours required for impregnation and cooking in the furnace) and the possibility to proceed with assembly immediately after winding.
Obviously, some precautions are needed in order to avoid quality issues:
- Use of insulation suitable for the temperature: cables, tubing and binding wires
- Slot insulation and between windings, made of material impregnated with self-bonding paint to allow total adhesion with the winding and avoid sliding which, due to the effect of magnetostriction, may cause failures in the long run
- Final head molding, since no changes can be made after bonding. In this regard, after molding, it is necessary to block the windings with suitable systems like: heat-resistant cages, binding with heat-shrinkable wire (preferred system), or, at minimum, molding press during the operation. The molding press, however, can be removed only after the windings have cooled.
- Another point to consider is the type of terminals that allow good contact (which our machines guarantee). For example: wires, FASTON or dedicated terminals, given the high circulating current.
