Which kind of dielectric material is better for the filtering capacitor?

In power electronic devices, the performance of the filter capacitor directly affects the stability and energy efficiency of the system. As the core component of the filter capacitor, the selection of the dielectric material directly determines the electrical performance and service life of the product. So, which dielectric material is better for filter capacitors?

I. Characteristics and Advantages of Metalized Polypropylene Film Materials

Metallized polypropylene film is currently the most commonly used dielectric material for filter capacitors, and it has three significant advantages:

1. First of all, the dielectric loss tangent value (tanδ) being lower than 0.0005 can effectively reduce energy loss.

2. Secondly, it has excellent self-healing performance. After local breakdown, it can automatically restore insulation.

3. Furthermore, the temperature stability is excellent. The volume change rate within the temperature range of -40℃ to +105℃ does not exceed ±5%.

II. Application Scenarios of Polyester Film Materials

Polyester film dielectric has unique value in cost-sensitive filter capacitors:

1. Its dielectric constant (ε ≈ 3.3) is higher than that of polypropylene materials, which is beneficial for reducing the size of the components.

2. Excellent moisture resistance performance is achieved, with the insulation resistance retention rate exceeding 90% in an environment with a relative humidity of 95%. However, it should be noted that the tangent value of the loss angle of PET material (approximately 0.003) is significantly higher than that of MKP. Therefore, it is more suitable for low-frequency filtering scenarios with lower efficiency requirements, such as the EMI filtering circuits of ordinary household appliances.

III. Principles and Trends for Selecting Medium Materials

When selecting the dielectric material for filtering capacitors, the "four-dimensional evaluation" principle should be followed: electrical parameters should be evaluated based on losses and withstand voltage; environmental adaptability should be considered in terms of temperature range and moisture resistance; economic performance should be assessed in terms of cost and lifespan; and special requirements should take into account high-frequency or pulse characteristics.