Filtering function and features of capacitor

Filtering function of capacitor

Eliminate the AC component in the rectified DC voltage. Absorbs the ripple current generated by the rectifier and inverter. The rectifier circuit turns the AC into pulsating DC, and after the rectifier circuit, a capacitor of larger capacity is connected to make the pulsating DC voltage after rectification into a relatively stable DC voltage by using its charging and discharging characteristics. Suppress the over-surge voltage generated by the switching process of the inverter part. Reduce the DC bus impedance.

Energy storage function of capacitor

When the motor is under decelerated condition, the motor speed is greater than the synchronous speed corresponding to the fr4quency converter output frequency, the motor is in the power generation state, and the kinetic energy of the motor is fed back to the DC side through the diode connected in parallel with the IGBT to achieve braking. The capacitor on the bus plays the role of buffering reactive energy, in order to provide a channel for the reactive energy feedback from the AC side to the DC side.

Film capacitor features

1、Small volume, light weight, excellent self-healing performance, safe and reliable.

2、Metal shell with heat sink, dry structure, with good heat dissipation performance.

3、Adopt metallized polypropylene film, internal filling with thermal conductive potting material.

4、It is suitable for use in high current pulse circuit. Especially suitable for filter circuits after IGBT rectification.

Capacitor test 

Appearance explosion, bulging of aluminum shell, cracking of plastic outer sleeve, outflow of electrolyte, opening of safety valve or being pressed out, cracking of valve at the top of capacitor, serious corrosion of binding post, deformation and shedding of cover plate indicate that electrolytic capacitor has been damaged. Using multimeter to measure whether there is an open circuit or a short circuit, and  the capacity is obviously reduced and the leakage is serious. The final stable resistance measured by multimeter is small.