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Three phase ac voltage controllers
Three phase AC voltage controllers use thyristors fired in sequence to control output voltage. The thyristors are triggered after a delay from the natural commutation point, which is the starting point of each 60 degree cycle if diodes replaced the thyristors. The output voltage waveform is similar to phase-controlled converters but produces an AC waveform. Bidirectional current flows through two thyristors connected back-to-back in each phase, with the current switching directions between the positive and negative halves of the cycle. Thyristors turn off when their current falls to zero and turn on when the anode voltage is higher than the cathode voltage and a triggering signal is applied to the gate.
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Overview of three phase AC voltage controllers, presented by A. Josin Hippolitus.
Presentation of circuit diagram related to the three phase AC voltage controllers.
Thyristor operations, firing sequence, and current flow in controllers, emphasizing bidirectional behavior.
Waveforms produced by three phase AC voltage controllers showing phase control.
Expressions related to instantaneous input voltage per phase in an AC voltage controller.
Thank you note acknowledging the audience and concluding the presentation.
Another thank you note reiterating appreciation for the audience's attention.
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Three phase ac voltage controllers
- 1. Three Phase AcVoltage controllers A.JOSIN HIPPOLITUS, ASSISTANT PROFESSOR, SRM UNIVERSITY
- 2. Circuit Diagram A.JOSIN HIPPOLITUS,ASSISTANT PROFESSOR, SRM UNIVERSITY
- 3. Operation The thyristors arefired in sequence starting from 1 in ascending order, with the angle between the triggering of thyristors 1 & 2 being (one-sixth of the time period (°60T) of a complete cycle). The line frequency is 50 Hz, with T=1/f=20 ms. The thyristors are fired or triggered after a delay of α from the natural commutation point. The natural commutation point is the starting of a cycle with period, (60°=T/6) of output voltage waveform, if six thyristors are replaced by diodes. Note that the output voltage is similar to phase-controlled waveform for a converter, with the difference that it is an ac waveform in this case. The current flow is bidirectional, with the current in one direction in the positive half, and then, in other (opposite) direction in the negative half. So, two thyristors connected back to back are needed in each phase. The turning off of a thyristor occurs, if its current falls to zero. To turn the thyristor on, the anode voltage must be higher that the cathode voltage, and also, a triggering signal must be applied at its gate. A.JOSIN HIPPOLITUS, ASSISTANT PROFESSOR, SRM UNIVERSITY
- 4. Waveforms A.JOSIN HIPPOLITUS, ASSISTANTPROFESSOR, SRM UNIVERSITY
- 5. Expressions A.JOSIN HIPPOLITUS, ASSISTANTPROFESSOR, SRM UNIVERSITY Instantaneous input Voltage per phase
- 6. Thank You A.JOSIN HIPPOLITUS,ASSISTANT PROFESSOR, SRM UNIVERSITY
- 7. Thank You A.JOSIN HIPPOLITUS,ASSISTANT PROFESSOR, SRM UNIVERSITY