Class 4 (4th Engineer) MET 📅 Jan 2024

Exam Question

(a) Shunt generators having drooping characteristics are best suited for parallel operation. Discuss. (6)

(b) Two 220 V d.c. generators each having linear external characteristics, operated in parallel. One machine has a terminal voltage of 270 V on no-load and 220 V at a load current of 35 A, while the other has a voltage of 280 V at no-load and 220 V at 50 A. Calculate the output current of each machine and the bus bar voltage when [10] the total load is 60 A. What is the kW output of each machine under this condition. (10)

Reference Answer

### Part (a): Suitability of Shunt Generators for Parallel Operation
DC Shunt Generators inherently possess a **drooping voltage characteristic**, meaning their terminal voltage decreases as the load current increases. This characteristic is not a flaw but a crucial feature that makes them exceptionally well-suited for stable parallel operation. The primary reasons are as follows:
1. **Stable Load Sharing:** The drooping characteristic provides a natural, self-regulating mechanism for load distribution.
* If one generator (Gen A) attempts to take on a larger share of the load, its output current increases.

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