For which applications is a DC motor chosen over an AC motor ?
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Answer: C. Variable speed operation
Explanation
DC motors allow precise and smooth speed regulation over a wide operating range. Varying armature voltage or field current provides straightforward control over rotational velocity. This flexibility makes them historically superior for applications requiring continuous speed adjustments. AC motors traditionally operated at fixed speeds dictated by supply frequency and pole count. DC motor speed is directly proportional to voltage and inversely proportional to magnetic flux. Modern power electronics have improved AC drives, but DC motors remain classic examples of control.
Paper mills, rolling mills, and printing presses require exact speed matching between multiple sections. Variable speed capability improves manufacturing precision and product quality in industrial plants. Choosing DC drives simplifies control systems where variable speed is the primary operational requirement. Low speed operation alone does not justify choosing DC motors over specialized AC gear motors. High speed operation can be achieved by various motor types including high-frequency AC designs. Fixed speed operation favors standard AC induction motors due to their simplicity and lower cost.
- Subject
- Engineering
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- Electrical Engineering
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- medium
Related questions
Q1. By inspecting which specific part can one easily identify a motor as a DC motor?
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Answer: C. Commutator
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Answer: B. increase in speed
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Answer: C. compound motor
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Q4. When a flywheel is used with a DC compound motor to minimize peak demand, what configuration must the compound motor have_____________?
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Answer: C. cumulatively compounded
A cumulatively compounded motor works effectively with a flywheel to smooth out severe peak demands. When load spikes, the motor slows down slightly, allowing the flywheel to release stored kinetic energy. This cooperati...
Q5. Why is a starter necessary when starting a DC motor___________?
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Answer: B. it limits the starting current to a safe value
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Q6. Which speed control technique is favored for constant torque drives ?
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Answer: B. Armature voltage control
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