Selection Skills Of Film Capacitors

Film capacitors have many excellent characteristics, so film capacitors are a kind of capacitor with superior performance. The insulation resistance of the film capacitor is very high, the frequency characteristic is superior, and the dielectric loss is small. This article introduces the selection techniques of film capacitors in detail. Hopefully the content is helpful to everyone.

The working principle of a film capacitor is the same as that of a general capacitor. It stores electric energy by storing charge on the electrodes, and is usually used together with an inductor to form an LC oscillating circuit. The working principle of the capacitor is that the electric charge will move under the force in the electric field. When there is a dielectric between the conductors, the electric charge will be prevented from moving and the electric charge will accumulate on the conductor, resulting in the accumulation of electric charge.

The following are what we should consider when selecting film capacitors:

1) Rated Voltage Of Capacitor:

Refers to the peak value of the high DC voltage or pulse voltage that can be continuously applied to the capacitor within the rated temperature range. Taking into account the reliability and derating requirements, it is usually required that the actual working voltage should be less than 80% of the rated voltage value.

2) Selection Of The Working Voltage Of The Capacitor:

Due to the loss of film capacitors, when used under high frequency and high pulse conditions, if there is a large current through the capacitor, the film capacitor will heat itself, and in severe cases there will be thermal breakdown (smoke, breakdown), etc. It is dangerous, so the current in use should be limited by the rated current of the capacitor.

When using, it must be ensured that these two voltages are both within the allowable range. If the actual working voltage (current) waveform cannot be determined, it can be determined by the self-temperature rise of the capacitor. Usually, for polyester capacitors, the self-temperature rise is allowed to be less than 10℃ under the conditions. For polypropylene capacitors, they are allowed to be used when their own temperature rise is less than 5℃. (The actual measurement should be tested on the surface of the lead welding part of the capacitor end surface)

3) Selection Of Capacitor Capacitance and Lead Span:

①Capacity selection must be within the range of E24 series values: 1.0, 1.1, 1.2, 1.3, 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.7, 3.0, 3.3, 3.6, 3.9, 4.3, 4.7, 5.1, 5.6, 6.2. There are 24 levels in 6.8, 7.5, 8.2, 9.1, and the horizontal line below is the E12 series value, which is the preferred series value.

②The capacitance value range should conform to the capacitance range given in the general specifications of various capacitors:

The specifications provided by different manufacturers may have slightly different upper and lower limits of the capacitance. However, if the selected value of the capacitance is lower than the lower limit of the category, it should be selected from ceramic capacitors. On the contrary, if the capacitance value is higher than the upper limit of this category, it should be selected among electrolytic capacitors.

③Selection Of Lead Forming Pitch:

For film capacitors of different types and specifications, the conventional lead pitch P has a certain value in the manufacturer's specifications, but in actual use, according to the PCB assembly requirements, you may require a manufacturer to customize the pitch F after the formation is given. 

The above content is about the selection skills of film capacitors. If you don't understand, you can consult an experienced manufacturer to help you with the selection.

Dongguan Zhixu Electronic Co., Ltd. (also JYH HSU(JEC)) has a full range of varistor and capacitor models with guaranteed quality. JEC has passed ISO9001:2015 quality management system certification; JEC safety capacitors (X capacitors and Y capacitors) and varistors have passed national certifications of the main industrial powers across the world; JEC ceramic capacitors, film capacitors and super capacitors are in compliance with environmental protection indicators. We have over 30 years of manufacturing experience. If you have technical questions or need samples, please contact us.