In a TSR, a thyristor exhibits a maximum average current 1000A for a conduction angle of 180°. Assuming the current waveform to be half cycle sine wave, find the corresponding maximum average current corresponding to conduction angle 60°.

In a TSR, a thyristor exhibits a maximum average current 1000A for a conduction angle of 180°. Assuming the current waveform to be half cycle sine wave, find the corresponding maximum average current corresponding to conduction angle 60°. Correct Answer 565A

By definition, the form factor (F.F) of half cycle sine wave for any conduction angle Φ is given by F.F = IRMS / IAVG ………………………………………………………….(i) => F.F = √/ /(1-cosΦ)……………………..…(ii) Putting Φ = 180° in equation (ii), F.F = ∏/2…………..………….(ii) In the problem it is given that IAVG = 1000A Therefore, from equation (i) RMS current rating of the thyristor, IRMS = 1000*(∏/2) = 1570A When Φ = 60°, from equation (ii), F.F = 2√ = 2.78 Since RMS current rating of the thyristor cannot be exceeded, Therefore, IAVG = 1570/2.78 = 565A (approx)