Half-Wave Rectified Current

Half-wave rectified current pulses. HWRC is achieved by removing all the negative cycles from AC waveform allowing the positive half cycles or vice versa to remain. This current waveform may be considered to be a form of DC due to the associated characteristics, with the additional advantage of a pulsating wave.

Fig. 10.3 Half-wave rectified current (single phase)

Since HWRC will leave a component partially magnetised, it is usually packaged as an AC/HWRC unit so that the AC may be utilised for demagnetisation.

Advantages include:

• Will detect sub-surface discontinuities.
• Will detect fine surface breaking discontinuities.
• Simple, effective, and inexpensive current form to achieve.
• Due to pulsating current, magnetic particles will vibrate and provide greater attraction to flux leakages. As such, dry powders or inks may be used with this waveform.

Disadvantages:

• May leave the part partially magnetised