Inverter control system which dynamically varies a voltage vector applied to the inverter based on primary flux and torque deviations

Claim 1

An inverter control system for operating a multi-phase induction motor by controlling primary magnetic flux generated on a stator of said motor and output torque of said motor in accordance with a primary flux command value and a torque command value, respectively, said system comprising: flux vector calculation means for calculating a primary flux vector from primary voltage applied to said motor and primary current flowing through said motor; torque calculation means for calculating an instantaneous torque value from said primary flux vector and said primary current; primary flux deviation calculation means for calculating a primary flux deviation of said primary flux vector from said primary flux command value; torque deviation calculation means for calculating a torque deviation of said instantaneous torque value from said torque command value; phase angle calculation means for calculating a phase angle of said primary flux vector; pulse generation means for generating a pulse signal which alternates cyclically at a time interval that depends on said primary flux deviation or torque deviation; control flag generation means for producing in response to said pulse signal a first control flag as a command of increasing or decreasing magnitude of said primary flux vector based on said primary flux deviation and a second control flag as a command of increasing, decreasing or retaining said instantaneous torque value based on said torque deviation; and voltage vector generation means for producing a voltage vector to be delivered to said inverter based on said phase angle and said control flag.