CONTROL OF ROTARY-FIELD ELECTRIC MACHINES

摘要

Disclosed is an arrangement for producing, in a rotary-field electrical machine, a stator current vector having an effective position between actual positions. The arrangement produces a stator current vector which can occupy alternately two adjacent actual positions at respective opposite sides of an effective position, and controls the durations for which the vector occupies the two adjacent actual positions thereby to control its effective position. A first signal generator generates a first periodic signal synchronised with the frequency of the electrical machine stator current, a second signal generator generates a second periodic signal having a higher frequency than the first periodic signal and a comparator coupled to the first and second signal generators compares the values of the first and second periodic signals. A change-over switch is arranged to be controlled in dependence upon the comparator for switching the stator current vector between the two adjacent actual positions in dependence upon the relationship between the values of the first and second signals.