What is the primary factor influencing mechanical losses in DC machines____________?
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Answer: C. speed
Explanation
Mechanical losses comprise bearing friction and windage resistance against rotation. Frictional forces scale directly with the rotational speed of the machine. Windage power losses increase rapidly at higher operating speeds. Rotational losses remain relatively constant for a given operating machine speed. Lubrication quality and bearing design influence total mechanical friction losses. Windage depends on rotor geometry and cooling fan aerodynamic drag characteristics.
Efficiency calculations require accurate separation of mechanical, core, and copper losses. High-speed turbine generators require specialized bearings to manage mechanical losses. Variable speed drives experience changing mechanical loss profiles across operational ranges. Current influences copper I squared R losses rather than mechanical friction. Voltage levels determine core losses and excitation power rather than mechanical drag. None of the above is incorrect because speed directly drives mechanical losses.
- Subject
- Engineering
- Category
- Electrical Engineering
- Topic
- —
- Difficulty
- medium
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