Abstract: An induction motor vector control apparatus employing a rotating Cartesian coordinate system (d,q) having a d-axis held in coincidence with a secondary flux of the induction motor. Another rotating Cartesian coordinate system (.gamma., .delta.) having a .gamma.-axis held in coincidence with the induction motor primary current to detects a .delta.-axis induction motor primary voltage change caused by a change in the induction motor secondary resistance. The .delta.-axis primary voltage change contains no component related to a primary resistance change and it is used to compensate the secondary resistance for its change.

Abstract: A process for producing pitch-type carbon fibers, which comprises melt-spinning pitch material in a gaseous atmosphere to form pitch fibers, gathering the pitch fibers in the presence of an oiling agent into a tow, followed by infusible treatment, carbonization treatment and, if necessary, graphitization treatment, of the tow of pitch fibers, characterized in that the tow of pitch fibers is brought in contact with a washing liquid to wash the surface of the pitch fibers prior to the infusible treatment.