Engineering Board Exam Reviewer · Three-Phase Systems in Power Applications · hard
A balanced three-phase resistive load is connected in delta. One of the three line wires opens. Compared with the original total power, the power now absorbed is
- one-third
- two-thirds
- unchanged
- one-half
Answer
D. one-half
Solution
With one line open, the phase between the two remaining lines has one resistor R in parallel with the other two in series (2R): Req=2R/3. The power is VL2Req=3VL2/2R, while originally it was 3VL2/R. The new power is one-half of the original.
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