It's a bit like they are all connected together by gears. All the generators are in phase. The most difficult bit for an operator is to make sure the generator

It's a bit like they are all connected together by gears. All the generators are in phase. The most difficult bit for an operator is to make sure the generator is synchronized before they actually connect it. Only after it's synchronized can they start actually feeding power in. You can't just turn these things on and off at will like a regular motor. To extend the gears analogy, gears need to be synchronised before they can engage - just like synchronous AC generators.