Motor control apparatus for a sewing machine

A motor control apparatus for a sewing machine comprising:

• an induction motor having a stator coil and a rotor for moving a needle in upward and downward direction;
• an inverter circuit for energizing said stator coil;
• an inverter controller for controlling an activation of said inverter circuit and for generating a rotating magnetic field in said induction motor;
• a command means for outputting a start command and a stop command of said induction motor to said inverter controller;
• a detector for detecting a predetermined position of a needle and outputting a position signal thereof to said inverter controller;
• and
• wherein said inverter controller includes;
• memory means for storing a predetermined set of activation control data representing voltage vectors relative to the rotating magnetic field and an activation time period relating to said voltage vectors;
• activation control means responsive to the start command for sequentially reading said set of activation control data from said memory means at an interval of a first predetermined period and for sequentially generating the rotating magnetic field within said induction motor in response to said set of activation control data read from the memory means to move said needle in upward and downward direction;
• and
• stop control means for maintaining the direction of the rotating magnetic field in an energizing state of said stator coil during a second predetermined period, utilizing the activation control data corresponding to the position signal received after issuance of said stop command from the command means.