Development of insulating ptfe film for mutual inductor

Transformers are often used to provide current and voltage signals to electric energy measurement, measurement, control, relay protection, etc. Their accuracy and reliability are closely related to the safety, stability and economic operation of the power system, and are one of the important high-voltage equipment in the power system. With the development of the power industry, the transmission capacity of the power system is increasing, and the operating voltage level of the power network is getting higher and higher. With the continuous improvement of the voltage level, the transformer is faced with the problem that the insulation structure is difficult to meet the operation requirements in the manufacturing.

As is known to all, polytetrafluoroethylene (PTFE) because of their excellent performance (class c insulation), chemical corrosion resistance, weather resistance, mechanical properties and thermal stability of the extraordinary, heat-resistant performance of ultra wide (use for a long time working temperature 150 ℃ ~ + 260 ℃), etc., in the field of electronic appliances, wire and cable, insulation has been more and more widely used. PTFE membrane can be used between the transformer winding copper foil, insulation and adhesive, through the film for improve the insulation class of transformer, reducing the gap between the layers of transformer and can enhance the mechanical strength of transformer, in addition, PTFE membrane can be used for dry type transformer, capacitor, electric instrument, such as gasket between the layers of insulation and heat-resistant electromagnet, line installation, heat insulation of the wire, has the very broad market prospect. The preparation method and performance research of PTFE film for mutual inductor insulation are also paid much attention by many domestic and foreign scientific research workers and processing enterprises. In this paper, the preparation method of PTFE film obtained from actual production and operation is studied through experiments.

1. Preparation of PTFE film

1.1 Choice of resin

The polytetrafluoroethylene (ptfe) film resin used for processing mutual inductor insulation shall be suspended resin with uniform molecular weight distribution and high crystallinity, generally with the crystallinity above 98 and molecular weight at 1O ~ 1O.The resin particle size is about 30t~m. PTFE of this specification is used to prepare PTFE film for mutual inductor insulation with excellent physical properties and excellent electrical properties.

1.2   Production process of ptfe film

(1) pretreatment of PTFE raw material

PTFE suspended fine resin was placed in a constant greenhouse at 20℃ ~ 23℃ for 24 hours for pretreatment.

(2) ramming and sifting

The pre-treated PTFE suspended fine resin was pounded and sifted by the rammer to make the resin loose for molding.

(3) the mold

Adopt cold pressing process method, add 10000gPTFE suspended fine material resin into the mold, press the blank with 20MPpa molding single pressure on the 100 ton automatic pressure machine, pay attention to exhaust during the pressing, and avoid the crack of the blank.

(4) sintering

Put the pressed products into high temperature sintering furnace, to 50.C/h rate of temperature rise to 330℃, insulation for 3h, then at 30℃ / h rate of temperature rise to 380℃, insulation 1O ~ 14h, and then at 30~40℃ / h rate of temperature drop to 320℃, insulation for 3 ~ 4h, finally at 50℃ / h rate of temperature drop to 150℃, turn off the electricity natural cooling to room temperature, take out the product.

(5) rotary cutting into film

The sintered preforms are turned into thin film preforms by special lathe. The membrane blank is 0.2mm×255mm×300m(thickness × width × length).

(6) calendering orientation

After rotary cutting, the directional blank is processed by the hot roll directional calender (see figure 2), and the directional degree is 1.8 ~ 2.0. The thickness is 0.1mm directional film, hot roll temperature control in 15O℃ ~ 180℃.

(7) cutting

Let's make the thickness 0.1mm directional film with special cutting machine processing into 0.Ptfe film for insulation of mutual inductor 1mm×35mmx 450 ~ 500m(thickness × width × length).

(8) inspection of packaging

Polytetrafluoroethylene (ptfe) film for insulation of the processed ct shall be sampled for internal performance inspection, and the appearance and size inspection of the film shall be conducted at the same time. PVC film bag shall be used for packaging of the products that pass the inspection, and inspection certificate shall be attached.

2.2 performance index of PTFE film

In this experiment, PTFE films with different orientation degrees (orientation degree of material, whose value is the ratio of the length of film samples before and after heating) are compared with standard indexes in tensile strength, elongation at break, dc breakdown voltage intensity and other properties.