Abstract: A ferrous metal inspection device particularly for elongated parts provides high intensity DC magnetic fields in each of two modes contemporaneously. One mode is generated by passing a DC current axially through the part to be inspected and the other is generated by a separate DC current passing through a pair of electromagnet coils positioned one at each axial end of a part to be inspected. Magnetic field lines are thereby generated in a pair of mutually orthogonal planes. Control and polarity of the two direct currents is effected by controlling the phase of conduction of separate corresponding silicon controlled rectifiers. The part to be inspected is drenched with a mixture of fine ferrous particles in a liquid vehicle. Solenoid wound coils connected in series or parallel are placed, one at each end of the part and a third coil surrounds the part circumferentially, thereby producing two substantially orthogonal magnetic fields.

Abstract: A system for controlling AC power for any load in which it is desired to limit and/or specifically program current at least for an initial period. SCR switches are employed, these being controlled as to angle of conduction out of the 180 degrees of each AC half cycle. The positive and negative half cycles are separated in a diode bridge and are separately handled throughout to the SCR's, which are connected two in parallel, in opposing polarity per phase. Voltage ramps are generated for each half cycle and a comparison circuit acts as a pick-off to start the SCR gate at a point in the half cycle determined by the comparator reference, the latter being the independent control. Fast turn-on leading edge spikes on the SCR gates are provided to minimize SCR di/dt stress.