How to solve the deviation of film capacitor

I believe that everyone has encountered the film capacitor deviation, then can you remedy this time? The answer is of course, the editor lists a series of solutions for your reference.

1. The capacity of the core after the flattening and setting is measured, and the offset center value is adjusted in time.

2. Track the distribution status of the finished product capacity and find out the error and timely feedback to adjust the capacity correction value.

3. Accurately determine the center value of the winding capacity (also called the correction value), and the rate of change of the process capacity such as heat (cold) pressure, heat treatment and encapsulation must be included in the capacity correction value of the core. The correction values are different for different models, different specifications and even different winding machines.

4. Timing and measuring the capacity and height of the core during the winding process to control the dispersion of the capacitance. If the product is tested after a short period of time, the product will be stored for a period of time, the capacity will change, resulting in an excess capacity. The polyester film capacitor is more obvious and generally shifts to the positive direction.

The solutions are as follows:

According to the variation law, the deviation value is controlled during the test, for example, the polyester film capacitor is clamped in the positive deviation, and the negative deviation is relaxed.

The manufacturing process causes process factors that cause variations in capacitance.

The product is heat treated once again after encapsulation.

After the encapsulation, it is naturally stored for one week before testing.

The capacitance of the wound film capacitor C = 0.177 ε s / d ε is the dielectric constant of the medium s is the effective area of the plate d is the thickness of the medium. The capacitance is proportional to ε and s and inversely proportional to d.

Although the document has been precisely specified, all three parameters will change during the process, resulting in capacity deviation. The focus of the process is to reduce these deviations and increase the capacity hit rate.

Winding process: There is an error in the width, thickness or margin of the film layer itself. The tension of the film changes from a large circle to a small circle, and the error of the tension of each winding machine. The pressure of the press roller is too small. The winding process is biased and the wrong side is wrong. When the humidity of the air is high, the core capacity is too large.

Hot pressing process: the core thickness error is unevenly applied, resulting in a tight core and a small capacity dispersion. The hot platen is not flat.

Temperature error. Heat treatment time or temperature error, internal impregnation, vacuum error, time error, and curing temperature error.

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