PULSE WIDTH MODULATED IGBT AC CHOPPER

A new circuit is presented for three-phase voltage controller (AC chopper) constructed from IGBTs. Traditionally such an equipment contains thyristors as switching elements. All drawbacks of this solution come from its only possible control method: firing control. The new circuit allows Pulse Width Modulation (PWM) control, providing much better properties. A new and advantageous control method is presented, including the protections also. Many application fields can be found, all require AC voltage control. The examined ones are: Energy-saving control of induction motor drive; Compensation of an unbalanced supply; Active filtering of the upper harmonics; Excitation system of brushless motor