Three-phase full converter with highly inductive load A 3-phase full converter feeds a highly inductive (continuous current) load with an average load current of 150 A. What is the peak current through each thyristor device?

Introduction / Context:
In a three-phase full-controlled bridge (six-pulse) converter with a highly inductive load, current is nearly constant and continuous. Each thyristor conducts for 120 electrical degrees carrying the same magnitude as the DC load current during its conduction interval. This question tests understanding of device current in continuous conduction.

Given Data / Assumptions:

• Converter: 3-phase full bridge, six SCRs.
• Load: highly inductive, thus current ripple is small and continuous.
• Average load current I_load,avg = 150 A.

Concept / Approach:

With continuous current, the DC link current equals the instantaneous device current whenever a device conducts. Each SCR pair conducts 120°, and current commutates from one device to the next without significant overlap (idealized). Therefore, the instantaneous (and hence peak) current in any conducting thyristor equals the DC load current.

Step-by-Step Solution:

Verification / Alternative check:

Circuit waveforms from standard analyses show flat device current pulses of width 120° at the DC current level for high inductance loads.

Why Other Options Are Wrong:

75 A or 50 A imply sharing between parallel devices in one arm, which does not occur; 300 A suggests both devices in series carry doubled current, which is incorrect.

Common Pitfalls:

Confusing RMS with peak; in this idealized case, peak equals the DC level because the waveform is nearly flat during conduction.

Final Answer:

150 A