Do Large Generators Really Use Permanent Magnets?

[cj]

I frequently teach my students about how basic generators work (motional EMFs, Faraday's Law, magnetic flux, etc.).

Question: do the generators used at large power plants really use a permanent magnet as a source of the magnetic field?

I was thinking that maybe an electromagnet might be used as the source, but I'm not sure. Plus I'm thinking that providing the electricity to this kind of electromagnet might significantly offset the generated electical energy that is produced.

[Averagesupernova]

The field is an electromagnet. This is the way the voltage is regulated by varying the current in the field.

[CraigHB]

For generators and motors, how practical is using a permanent magnet with repsect to an electromagnet? In other words, how does the efficiency and power generation compare?

[MisterX]

I found this link (http://www.windturbines.net/wiki/Synchronous_Generators). The author(s) of that page have claimed higher efficiency for permanent magnet synchronous generators than for the wound rotor type. But there are other issues with permanent magnet synchronous generators.

I have read the development of high energy permanent magnets (such as Nd2Fe14B magnets) have made permanent magnet synchronous generators more competitive with other types of generator.