TABLE OF CONTENTS Paul N. Worsey, Jason Baird, and Jahan Rasty
The armature is part of the electric circuit within the generator, and as the flux within the generator is compressed, electric currents flow on the outer surface of the armature in a helical direction due to the magnetic field orientation. The flow of these currents must not be disturbed. If their flow direction is altered, the magnetic field direction will be affected. If features on the surface of the armature retard the current flow an arc can form between the armature and the stator or simply the armature/helix contact cannot progress smoothly, cf. Chap. 5.4.1. In the extreme case, the arc will create a hot plasma, which can cause the stator insulation to break down before the contact edge reaches that location. Since arcing causes current flowing from the armature to the stator to jump ahead of the contact edge and the contact is no longer part of the current path, compressed magnetic flux is trapped in the region between the sliding contact and the arc, thus lost for further compression [Kno70].
Longitudinal cracking in the surface of the expanding armature interferes with electrical currents generated on the surface of the armature, affects the generation of plasma in the sliding contact area, and causes magnetic flux to be trapped within the sliding contact area. Trapping of the flux within the contact area, called "flux cut-off' in the idiom of flux-compression generators, does not allow the flux...
