Electricity sabotage: North Carolina Duke Energy Restores Power

Nope. Probably AC. Something for a home is probably AC, rectified to DC, then converted back to AC in sync with the grid. Why? Producing DC requires a generator with a commutator and brushes. Those become wear items that need to be replaced from time to time, and produce quite a bit of dust as they wear. Needless to say, performing maintenance at the top of a 30 foot mast is hard enough. At the top of a 300 foot mast is considerably harder. Better to use an alternator that doesn’t have a commutator and brushes.

Large scale windmills might use a more sophisticated alternator that is able to directly sync with the grid.





I agree with Peter that turbines are AC generators. But I think how a large wind turbine works is a bit more complicated. In order to connect to the grid it has to be generating AC that is 60 Hz. There seems to be two ways to handle this.

  1. The turbine spins at an unknown and variable frequency. So they must convert it to DC, then back to AC sync’ed to the grid.
    See this link below.
    But the grid is also 3 phase in a delta configuration. So they have to generate all 3 phases or possibly use output from 3 turbines to do this. A small home-sized turbine could be just a single phase.


  1. In the second method, a governor controls the speed of the turbine so that the output is 60 Hz
    wikipedia claims this is how it has been since 2003



If wind turbines generate AC, I would expect it to be polyphase AC. The grid in only three phase. Single phase means current goes to zero. Three phase helps fill in the gaps. Polyphase is best. I hear Pennsylvania Railroad was/is polyphase.

We have noted before that the US grids are not all in phase. For NJ to buy power from Maryland they have to do a phase shift.

They do talk about the good old days of motor generators to convert from one system to the other. Now days electronics is the way.

I couldn’t find the Wikipedia page on the NJ phase shift installation but I did find this one:

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Good lord, you engineering guys get lost in the details awfully quickly.

For us lay people, knowing that the wind turbine initially generates AC is probably good enough. The next level of knowledge might be to add that there are some exceptions in home installations that start with DC. About the most you need to know if you’re not designing a system is that the initial AC is probably not going to be in sync with the grid, so it will either get converted to DC then back into properly synchronized AC, or be directly converted through the magic of modern electronics so that it IS in sync with the grid.

Anything beyond that is for the electronic engineering classroom, then put into practice in the gory details of individual system design.