Abstract: Magnetizing current supplies are disclosed for supplying current for magnetizing parts in a magnetic particle inspection system, including SCR's connected in circuit with a three-phase voltage step-down transformer to accurately control the duration and magnitude of magnetizing current. In one type of supply, six SCR's are connected between magnetizing apparatus and terminals of three center tapped secondary windings of a three-phase voltage step-down transformer, the SCR's being operable to rectify current and also being connected to a phase control circuit which controls firing times of all SCR's to control the magnitude of the magnetizing current.

Abstract: Demagnetizing methods and apparatus are provided in which a pipe, tube, rod, bar or other elongated part to be demagnetized is moved through the coil assembly to which pulses of current are applied to produce magnetic field pulses of alternating polarity and of substantially constant durations and magnitudes with a substantially constant repetition rate, each current pulse being effective to produce by the end thereof a reversal of the magnetic field in all portions of the part positioned within the confines of the coil assembly and immediately adjacent thereto, the part being moved longitudinally through the coil assembly at a velocity sufficiently low as to effect demagnetization of all portions of the part. The duration of each current pulse is at least 50 milliseconds and most preferably on the order of 0.5 seconds and the velocity of movement is preferably less than two feet per second.