AExE01 · Chapter 1Basic Electrical & Electronics🏛️ Past Licensure QuestionID: 2030eb0a
A large commercial three-phase generating system has an electrical efficiency of around:
A large commercial three-phase generating system has an electrical efficiency of around:
Multiple Choice Options
- A✓ Correct Option
96%
- B
90%
- C
67%
- D
55%
Detailed Technical Solution & Explanation
Large three-phase alternators (synchronous generators) in modern power stations are highly efficient machines, typically achieving full-load efficiencies between 95% and 98% (averaging ~96%) due to low stator resistance and optimized laminated core designs.
Option Analysis:
•
Option A (96%): Correct. Large 3-phase generators routinely achieve 95%–97% operating efficiency.
•
Option B (90%): Incorrect. Typical for smaller induction generators, but below standard for 3-phase utility generators.
•
Option C (67%): Incorrect. Unacceptably low for any commercial electrical power generator.
•
Option D (55%): Incorrect. Thermal steam plants have ~35–45% thermodynamic cycle efficiency, but the electrical generator itself operates at ~96%.
Reference: Mock Test 01NEC Licensure Syllabus