Analysis of dielectric loss characteristics and their influence on IGBT buffer film capacitors

1. Mechanism of dielectric loss
When the IGBT Snubber Film Capacitor is in an external electric field, the insulating material (i.e., film dielectric) inside it absorbs and scatters the signal in the electric field. This process not only causes the loss of signal energy, but is also accompanied by energy conversion and dissipation. This energy consumed per unit time due to the electric field is called the loss power of the dielectric, or dielectric loss for short. The generation of dielectric loss mainly stems from the microstructural characteristics inside the insulating material and the polarization process under the action of the electric field.

Under the action of the electric field, the dipoles inside the insulating material will be oriented and polarized. However, since the movement of the dipoles needs to overcome a certain resistance, the polarization process is not completed instantly, but there is a certain hysteresis effect. This hysteresis effect causes the electric field energy to be lost in the process of converting to heat energy, i.e., dielectric loss.

2. The influence of dielectric loss on capacitor performance
Dielectric loss has many effects on the performance of IGBT Snubber Film Capacitors. First, dielectric loss causes the capacitor to heat up during operation and increase its internal temperature. If the temperature continues to rise, it will not only reduce the insulation performance of the capacitor, but also may cause thermal aging of the dielectric material, thereby shortening the service life of the capacitor.

Secondly, dielectric loss will increase the equivalent series resistance (ESR) of the capacitor and reduce the effective utilization rate of its capacitance value. This will cause the performance of the capacitor to deteriorate under high-frequency applications, affecting the switching speed and efficiency of the IGBT. At the same time, the increased ESR may also cause resonance in the circuit and interfere with the normal operation of the circuit.

In addition, excessive dielectric loss may also cause capacitor breakdown failure. When the dielectric loss causes the internal temperature of the capacitor to be too high, the insulation performance of the insulating material will drop sharply. At this time, if the voltage borne by the capacitor exceeds its rated voltage value, it may cause a breakdown failure, resulting in damage to the capacitor, and even cause a short-circuit failure of the circuit system.

3. Measures to reduce dielectric loss
In order to reduce the dielectric loss of the IGBT Snubber Film Capacitor and improve its performance stability, the following measures can be taken:

Select low-loss dielectric materials: Selecting insulating materials with low-loss characteristics as the dielectric layer of the capacitor can effectively reduce dielectric loss.
Optimize capacitor structure: By optimizing the structural design of the capacitor, such as increasing the thickness of the dielectric layer and improving the contact interface between the electrode and the dielectric, the dielectric loss can be reduced and the stability of the capacitor can be improved.
Control the working environment: Maintaining the stability of the working environment of the capacitor and avoiding the influence of adverse factors such as excessive temperature and excessive humidity can help reduce dielectric loss and extend the service life of the capacitor.
Regular inspection and maintenance: Regular inspection and maintenance of the capacitor to promptly detect and deal with potential fault hazards can ensure the long-term stable operation of the capacitor.