General:
* Dynamo
* Alternator
* Power generator
* Electricity generator
More specific:
* Magneto (for small, self-contained generators)
* Turbogenerator (for generators powered by turbines)
* Hydroelectric generator (for generators powered by water)
* Wind turbine (for generators powered by wind)
The best word to use will depend on the specific situation and the level of detail you want to convey.
