According to Baidu Library, polyester film capacitors are usually used for bus capacitors in low frequency applications. Polyester film capacitor has the characteristics of high capacitance and low loss tangent, which is an ideal choice for low frequency applications. Bus capacitance is usually used for power filtering and bus connection in capacitor banks. Polyester film capacitor can provide higher capacitance value, which is helpful to reduce voltage fluctuation and current noise in power filter. In addition, the polyester film capacitor has high stability and reliability, which makes it an ideal choice for bus capacitor applications.

However, in high frequency applications, polyester film capacitors will have the problems of unstable capacitance and high loss tangent. Therefore, in high frequency applications, other types of capacitors, such as ceramic capacitors or air capacitors, are usually used.