The principle behind regenerative braking relies on the fact that___________?
Show answer Hide answer
Answer: C. back e.m.f. of rotor is more than the applied voltage
Explanation
Regenerative braking happens when the motor speed exceeds the synchronous or no-load speed threshold. This increased rotational velocity forces the induced back electromotive force to surpass the applied terminal voltage. When the generated voltage exceeds the supply voltage, electrical power reverses direction and flows back into the grid. Direct current motors function seamlessly as electric generators whenever mechanical driving torque overrides electrical input torque. Faraday's law of induction governs the magnitude of the generated back electromotive force based on rotational speed. Energy recovery systems capture kinetic energy efficiently to reduce overall power consumption in modern transportation systems.
If the back electromotive force remained less than the applied voltage, the machine would continue operating purely as a motor. An equal voltage condition results in zero armature current flow, halting net power transfer between source and load. Selecting none of the above ignores the fundamental condition where generated voltage exceeds supply voltage during braking.
- Subject
- Engineering
- Category
- Electrical Engineering
- Topic
- —
- Difficulty
- medium
Related questions
Q1. Mechanical power output from a shunt motor reaches its peak when the ratio of back e.m.f. to terminal voltage equals______________?
Show answer Hide answer
Answer: D. 0.5
Mechanical power output in a shunt motor equals armature current multiplied by back emf. Calculus derivation proves that power reaches its peak when back emf equals terminal voltage. Dividing back electromotive force by...
Q2. The armature torque produced by a D.C. shunt motor is directly proportional to____________?
Show answer Hide answer
Answer: B. armature current only
Armature torque in a direct current motor depends directly on both main field flux and armature current. In a shunt motor configuration, the field winding connects across a constant voltage supply source. Constant termin...
Q3. The resistance used during the starting phase of a D.C. motor is generally_______________?
Show answer Hide answer
Answer: A. low
A low starting resistance is crucial because it limits the initial rush of high current. Without this resistance, the motionless armature would draw destructive currents directly from the supply lines. The added resistan...
Q4. A three-point starter is suitable for operating______________?
Show answer Hide answer
Answer: D. both shunt and compound motor
A three-point starter includes a specialized protective coil connected directly in series with the shunt field circuit. This specific wiring arrangement allows the starter to safely energize and control shunt-wound direc...
Q5. When a motor's speed drops from 1100 r.p.m. at no-load to 1050 r.p.m. at full load, its speed regulation is______________?
Show answer Hide answer
Answer: B. 4.76%
Speed regulation measures the percentage speed drop from no-load to full load conditions. Subtracting full-load speed from no-load speed yields fifty revolutions per minute difference. Dividing this difference by the ful...
Q6. In a D.C. generator, iron losses primarily occur within___________/
Show answer Hide answer
Answer: D. armature rotor
Iron losses consist of hysteresis and eddy current losses occurring inside ferromagnetic core materials. The armature rotor experiences continuous magnetic field reversals as it spins between the stationary field poles....