Ripple current of film capacitor

Film capacitors are excellent capacitors because of their excellent characteristics. Its main characteristics are as follows: no polarity, high insulation resistance, excellent frequency characteristics (wide frequency response), and low dielectric loss. Ripple current is the higher harmonic component of the current, which causes a change in the current amplitude and may cause breakdown. Because it is an AC component, it will be dissipated in the capacitor. If the ripple component of the current is too large, it exceeds the allowable ripple current of the capacitor, which will cause the capacitor to burn. Ripple current refers to the RMS value of the AC current flowing through the capacitor, which appears as a ripple or ripple voltage on the voltage.

The film capacitor allows the ripple current to be controlled by ambient temperature, capacitor surface temperature, loss angle (or ESR), and AC frequency parameters. The heat loss from ripple will be a key reference factor for capacitor life. When the ripple current increases, the ripple voltage multiplies even when the ESR remains constant.

As the ripple voltage increases, the ripple current also increases, which is why the capacitor is required to have a lower ESR value. After the ripple current is added to the stack, the equivalent series resistance (ESR) inside the film capacitor causes heat generation, which affects the service life of the capacitor. The ripple current is proportional to the frequency, and the ripple current is also low at low frequencies. In addition, the rated ripple current is also called the allowable ripple current. This refers to the value of the AC ripple current that the film capacitor can withstand under high operating temperature conditions, and the specified ripple is the standard frequency (typically 100Hz--120Hz). Sine wave.