Whether it is a stator winding or a rotor winding, whether it is a soft winding or a hard winding, the ends of the windings will be bound during the manufacturing process. Theoretically speaking, the purpose of binding is to ensure that the relative positions of the windings remain unchanged, the windings and the insulation, and the windings and related components, and to help the curing effect after the windings are impregnated and dried.
To achieve this, heat-shrinkable insulating tape or binding rope is used when binding the windings to ensure that the ends form a relatively solid whole after the windings are impregnated and dried. However, the heat shrinkage of the binding tape has a certain range, so a certain tension should be maintained during the binding process.
It is also important to emphasize the issue of binding and securing the lead wires. On the one hand, it must be ensured that the lead wires cannot be moved arbitrarily after binding; on the other hand, it must be ensured that the connection between the lead wire and the main wire will not be subjected to pulling during subsequent processing. For these reasons, the binding of the winding ends must be standardized and cannot be merely a superficial wrapping.
Analysis of high voltage motor end binding application
Since motor windings can be in phase or out of phase, there will be mutual attraction and repulsion forces between the two wire bars of adjacent coils at the ends. In order to avoid displacement caused by the force, the ends need to be fixed. Polyester rope with a thickness similar to the gap size is selected and tied tightly in the side gap between adjacent winding wire bars.
Currently, high-voltage motor stators mostly employ the VPI (Vacuum Insulation) process. Its insulation structure involves wrapping the coil with mica tape, binding the coil ends with polyester fiberglass rope, and securing the coil to the end clamps with rope tension, but not too tightly, to prevent insulation damage at the contact points and subsequent reduction in insulation performance. When the coil is heated and wound according to process requirements, the insulation near the nose of the coil softens. This damages the insulation and affects its service life.
Because high-speed motors have large pitches and large pole-to-pole distances, stator windings generally have long end dimensions and large bell-shaped openings. Some also use large and small coils, with the inner circular coil at the end being wavy, and the gap between the upper and lower layers being extremely small. To address this, a 4-5mm thick layer of polyester felt can be wrapped flat on the coil end clamp insulation, acting as a padding between the coil and the felt. Because polyester felt is soft and has a certain amount of compression, it prevents the coil insulation, which is wrapped with wire, from being crushed by the end clamp. It also increases the contact area at the binding point, ensuring tight contact between the coil and the end clamp. After the varnish on the winding has cured, this will facilitate the radial and tangential fixation of the ends.
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