Who independently developed the self-exciting dynamo concept around the 1860s?

Answer

Samuel Alfred Varley, Charles Wheatstone, and Werner von Siemens

Samuel Alfred Varley is mentioned in connection with the development, followed by Charles Wheatstone and Werner von Siemens, who independently developed the self-exciting dynamo concept around the 1860s.

Who independently developed the self-exciting dynamo concept around the 1860s?
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