A superconducting magnet has an inductance of 4.9 H, a resistance of 3.6 m, and a rated

Question:

A superconducting magnet has an inductance of 4.9 H, a resistance of 3.6 mΩ, and a rated operating current of 80 A. It will be supplied from a 15-V rms, three-phase source through a three phase, phase-controlled bridge. It is desired to "charge" the magnet at a constant rate to achieve rated current in 25 seconds.

a. Calculate the firing-delay angle αd required to achieve this objective.

b. Calculate the firing-delay angle required to maintain a constant current of 80 A.