Recently a thyristor inverter is used for induction motor drive because of its controllability and economy. However its advent causes a few problems: ripples of torque, angular velocity and mechanical resonance due to harmonics of inverter output. Then torques are analyzed by means of the space vector that is produced by d-q component of squirrel-cage induction motor fed by current or voltage-type inverter. Besides, PWM patterns that have been used or considered are classified on the basis of the space vector and those characteristics are indicated.
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