A DC series motor must started on no load because it would
A. Fail to start without load.
B. Run at dangerously high speed.
C. Not develop starting torque.
D. Draw more current without producing sufficient torque.
Answer: B
Share your understanding of this question with the correct explanation.
A DC series motor must be started on no load because it would run at dangerously high speeds.
DC series motors have a characteristic called “runaway speed” or “dangerous speed” when operated without any load. This means that without a mechanical load to oppose its rotation, a DC series motor can accelerate to excessively high speeds, potentially causing damage to the motor or its driven equipment.
When a DC series motor runs at high speeds, it can experience mechanical stresses, increased wear and tear, and reduced efficiency. It may also become unstable and uncontrollable, posing safety risks to the surrounding environment.
By starting a DC series motor on no load, the motor is allowed to initially spin freely without any load torque applied. This prevents the motor from reaching dangerous speeds and provides an opportunity to gradually introduce and control the load once the motor has stabilized.
Therefore, the correct answer is B: Run at dangerously high speed. A DC series motor must be started on no load to avoid the motor running at dangerously high speeds, which can lead to various operational and safety issues.