The series field of long shunt compound generator is excited by

Question

Examoogle · Accepted Answer

Load current

Explanation: In a long shunt compound generator, the series field winding is connected in series with the armature, meaning it carries the full load current. This configuration ensures that the series excitation is directly proportional to the current supplied to the external load.

Working Principle: The armature current ($I_a$) flows through the series field winding before reaching the load. In this specific configuration, since the shunt field is connected across the entire armature output terminals (parallel to both series field and load), the series winding experiences exactly the load current ($I_L$). Consequently, as the load demand changes, the magnetic flux produced by the series field adjusts accordingly, which aids in maintaining the terminal voltage.

Key Formulas: $I_a = I_{se} = I_L$; $V = E_g - I_a(R_a + R_{se})$

Key Points: The series field is placed in the main line path, allowing it to sense the load current.; Long shunt generators provide better voltage regulation compared to short shunt under varying load conditions.; The shunt field winding is connected in parallel with the combination of series field and armature.

Advantages: Improved voltage stability under load; Self-compensation for voltage drop in the armature and series field

Disadvantages: More complex wiring compared to simple shunt generators; Higher internal voltage drop due to series field resistance

Applications: Power supply for DC motors; General purpose DC power distribution

Additional Info: In a short shunt compound generator, the series field carries only the load current, while the shunt field is connected directly across the armature.. Option D is incorrect because the armature current equals the load current only in this specific series configuration, but 'load current' is the more accurate descriptor of the excitation source for the series field.

Answer: C is correct — The series field in a long shunt compound generator is connected such that it carries the full load current.

Exam Tip: Remember that in 'long shunt', the shunt winding spans the 'long' distance across both armature and series field; in 'short shunt', it only spans the armature.

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