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Yangzhou Fongming Cable: Talking about the technology of wrapping wire

Views:0     Author:Site Editor     Publish Time: 2022-01-14      Origin:Site

The wire diameter, the width and thickness of the wrapping film, the overlap ratio, the wrapping pitch, and the wrapping angle of the composite insulated wrapped wire must be perfectly matched. At the same time, the stretching of the film must be considered in the structural design.

Most of the faults and damages of rotating electrical machines are caused by the damage of the winding insulation, of which the inter-turn insulation of the winding accounts for about 50%, and the damage will be serious. The inter-turn insulation short circuit is fundamentally caused by the inter-turn impulse voltage value of the motor exceeding the working voltage of the local winding inter-turn insulation under the action of various overvoltages. One part is formed by the mechanical damage of the coil and winding during the manufacturing process. There are also partial discharges generated by the internal gaps of the high-voltage motor windings and corona corrosion of the high-voltage windings. The damage caused by the above factors is directly or indirectly related to the performance of the winding wire used in the motor. With the upgrading of rotating electrical machines and the needs of various special motors and high-temperature motors, it is imperative to develop new types of winding wires (magnet wires).

Mica Wrapped Wire

In recent years, with the implementation of energy-saving policies, the domestic power grid has been upgraded to reduce line losses, and industrial and mining enterprises have chosen medium-sized 10kv motors to reduce investment in power distribution. To replace 6kv motors, the demand for medium-sized 10kv motors has increased significantly. One of the technical difficulties is the insulation between turns of the stator coil. Because the wires are often thin, it is difficult to wrap the mica tape by hand or machine. The self-insulation of the film-wrapped wire is used as the insulation between turns, which has poor corona resistance. Among the faults, inter-turn faults account for a large proportion, and the reliability of inter-turn insulation is also attracting more and more attention. Some users even specify high-voltage motors that require mica for inter-turn insulation.

The measures taken abroad in this regard are to generally use mica-wrapped wires, and use the insulation of the wire itself as the insulation between turns. In recent years, Harbin Institute of Technology and Shanghai Institute of Science and Technology have also conducted research on powder mica tape inter-turn insulation, and some magnet wire factories have also successfully developed mica wraps of various structures with the assistance of insulation material factories and motor factories. The wire was originally coated with polyester film or polyimide film on the optical wire, and then covered with a layer of powder tape or Tongma powder tape, covered with double glass fiber, and painted with self-adhesive paint, which was later used. The 1mm thick F-grade phenolic epoxy double-sided polyphenol film powder mica tape is wrapped with one or two layers, covered with thin double glass, and coated with self-adhesive paint. At present, many electrical machinery factories are in trial implementation.

High impulse withstand voltage between turns of mica-wrapped wire: single-layer mica-wrapped wire inter-turn insulation is equivalent to that of single-layer film-wrapped wire, each turn of 1.skV is charged three times, double-layer mica-wrapped wire inter-turn insulation is comparable to single-layer film-wrapped wire Each turn of the film-wrapped wire is equivalent to a half-stack of 5438-1-layer and a double-layered film-wrapped wire, and each turn of ZkV is charged three times.

High power frequency breakdown voltage of inter-turn insulation of mica-wrapped wire: The average value of power-frequency breakdown voltage of inter-turn insulation of mica-wrapped wire is greater than 20kV except for No. 1 sample covered with a layer of mica tape. The inter-turn insulation of the thin-film wrapped wire (see No. 9-11. No. 14-17) is below 20kV, while the old-fashioned double-glass wire pad mica structure is only a few kV. The double-glass wire-wrapped layer of mica tape structure is below 20kV , The double glass wire wrapped with two layers of mica is only 21kV.

The inter-turn insulation structure of mica-wrapped wire has good corona resistance: It is well known that mica has excellent corona resistance, so the inter-turn insulation of mica-wrapped wire is better than that of film-wrapped wire.

Mica-wrapped wire is an ideal wire for high-voltage motor stator coils. It is used to replace polyphthalimide film-wrapped wires, which can improve the reliability of inter-turn insulation and solve the difficulty of inter-turn mica tapes of medium-sized 10kV motors. It can also reduce costs. , the social and economic benefits are obvious.

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