With the continuous improvement of industrial automation, frequency converters have been more widely used, in which capacitors are indispensable. So what specifications of capacitors should be selected to be more suitable for use in frequency converters?
Frequency converter is a power control device that uses the on-off function of power semiconductor devices to convert power frequency power supply into another frequency. The frequency converter is mainly composed of rectifier (DC to AC), braking unit, driving unit, micro processing unit, etc. In capacitors, aluminum electrolytic capacitors and film capacitors are used in frequency converters.
Among the capacitor families, electrolytic capacitors, film capacitors, super capacitors, patch capacitors, ceramic capacitors, etc. are used in different fields.
Electrolytic capacitor plays an important role in frequency converter as a rectifier and filter capacitor. However, in the process of operation, the loss of aluminum electrolytic capacitors is very large, among which the reactive power loss can account for 20% of the total reactive capacity, and will increase with the increase of frequency. The loss is distributed in the form of heat, which leads to aluminum electrolytic capacitors being easier to heat up, shorter working time and higher failure rate. The damage of aluminum electrolytic capacitor often causes that the whole equipment cannot continue to operate.
Thin film capacitors have the advantages of non polarity, low dielectric loss, low parasitic inductance, low impedance, good temperature characteristics, small size, long working time, etc. In the same capacity, the ripple current resistance of the film capacitor is higher than that of the aluminum electrolytic capacitor. The low impedance of the film capacitor greatly reduces the voltage stress on the switch tube, which is conducive to the reliability and stability of the switch tube.
Compared with aluminum electrolytic capacitor, thin film capacitor is more suitable for frequency converter. The film capacitor can work for a long time in the process of use, and can be maintenance free in the frequency converter, which greatly saves maintenance costs and manpower, and avoids the trouble of replacing capacitors with inverter appliances and the cost increase. It is inevitable to replace aluminum electrolytic capacitor with thin film capacitor in frequency converter.