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Discussion on the relationship between mutual inductor and FR-4 epoxy plate

Today, someone called and asked, “what is the insulation material on the transformer?” Our customer service staff gave him a solution. It is not clear that we are not very clear, I search the Internet, almost no relevant introduction, I as a professional manufacturer, because of the time is tight, I simply help you analysis, also hope to fill this vacancy field on the Internet.

The insulation material on the inductor is FR-4 epoxy board. First, understand the working principle of the transformer.

epoxy glass sheet

It is also called an instrument transformer. Its main function is the partial voltage and the partial current, it can divide the voltage into about 100V, the rated current 5A, in order to measure the precision measurement of the instrument, and it also plays the role of protecting the electrical equipment, and it is convenient and safe to help people to work.

Next, I would like to know why the FR-4 epoxy board is used on the transformer.

1.  insulation, high dielectric; transformer in fact with the transformer’s working principle is the same, are based on electromagnetic induction principle. The winding N1 is connected to the measured current, and the N2 is connected to the measuring instrument, so its insulation should be very high, the vertical layer to the electrical strength (in the 90 + 2 C transformer oil, the thickness of the plate 1mm): more than 14.2MV/m; the parallel layer to the breakdown voltage (at 90 + 2 C transformer oil): more than 40KV, the general transformer voltage is only about 100V, for the breakdown of its root It can’t be, and there is no need to worry about it being broken into a conductor.

2. anti static electricity, and then the above problem, it produces a magnetic field, of course, there will be a current generation, there will be electrostatic phenomenon, especially in the dry winter, FR-4 epoxy plate relative dielectric constant (50Hz): less than 5.5; relative dielectric constant (1MHz): less than 5.5, it is good to prevent the occurrence of static electricity, conducive to personnel operation. .

3. excellent flame retardancy; with the construction of urbanization, high buildings are everywhere, but the fire is also frequent, giving people a huge loss of life and property, the position of mutual transformer of course equipment will also increase accordingly. If the transformer adopts FR-4 epoxy board as insulation material, the combustion time can be delayed and the rescue work can be saved time. Its flame retardancy reached the national 94V-0 standard.

4. high temperature resistance; if the two open circuit, the current transformer core flux is very strong, saturated, iron core heating, burning insulation, producing leakage; and FR-4 epoxy plate high temperature of up to 150 degrees, basically will not be burned, from the insulation material into conductor.

Finally, I will briefly understand other physical parameters of FR-4 epoxy board.
(1) water absorbency (D-24/23, plate thickness 1.6mm): less than 19mg;
(2) vertical layer bending strength A: normal: E-1/150150 + 5 340Mpa;
(3) insulation resistance (D-24/23) after immersion: greater than 5 x 108 ohm;
(4) insulation resistance (D-24/23) after immersion: greater than 5 x 108 ohm;
(5) density: 1.70-1.90g/cm.

I think you should know the relationship between the mutual inductor and the FR-4 epoxy board. Because the time is relatively close, if there are some unclear places, I can call me. I will make a detailed answer to the questions.

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