IEC 61000-3-2

Although the limit values shown below were taken from a previous edition (IEC 61000-3-2:2005+A1:2008+A2:2009), which is obsolete, they give a good impression of how electrical equipment is tested with the aim to reduce mains pollution, reduce transmission loss and mains voltage waveform distortion.

A 100 or 120 Hz ripple on the DC voltage is almost inevitable, especially in the early days of electronics, but it could give hum in speakers of audio equipment and vertical, slowly moving dark and light modulation on TV screens.

A simple and cheap means of getting low ripple is to use a relatively inexpensive electrolytic capacitor with high capacitance values, direct coupled after the mains voltage rectifier.

IEC 61000-3-2 aims to set limits to the harmonic currents drawn by electrical apparatus and so maintain mains voltage quality.

With present day components with wide use, e.g. in fluorescent lighting ballasts, the cost is relatively low.