Hi Roly -- I think they are just using variations of the normal terms that are not so common in the US.
Coercivity is what we usually talk about with magnets -- how difficult it is to make the material non-magnetic again, or change the polarity. Remanence is the opposite side of the magnet's BH curve -- how much magnetism is left when you remove the external field. Coercivity is shown as Hc.
The Maximum Energy Product (BHmax) is measured in MgOe (megagauss oersted, it's basically coercivity x remanence. It's the best measure of magnet quality. Magnet grades start with a letter (N for Neodymium, C for ferrite, etc.). The number after it is BHmax. An N48 grade magnet will be very expensive compared to an N35 or N40, but will only give a slight percentage increase in power in an alternator.
Neodymium (NdFeB) magnets are about the best choice for alternators....Samarium Cobalt is much more expensive and not quite as powerful, but is more resistant to heat. Not really an issue with wind turbine alternators (if your magnets are heating up, you have some BIG problems going on in your alternator!). No other formulations are as powerful as NdFeB, and none are even worth considering for an air gap alternator.
Cheers -- ADMIN
