2 ms·
Permanent magnet excitation is a possible way to generate the required field flux for a generator, but it's not a reliable way. If the permanent magnetic field
by mpyne 14y ago
Permanent magnet excitation is a possible way to generate the required field flux for a generator, but it's not a reliable way.
If the permanent magnetic field isn't strong enough you can't even generate enough voltage to power-up the excitation circuit at all, and that's the circuit which would feed the current back in.
So whether this is feasible or not depends on the generator design.
- femto 14y agoI've got memories of some of the Snowy Mountains scheme's hydroelectric generators being designed to start though self-excitation. Wikipedia also has a bit about it [1]. It seems that there is usually a backup facility to run a DC current though the field winding before starting, thus magnetising the magnetic paths, for when the residual field has decayed too much. That backs up your comments about reliability. [1] http://en.wikipedia.org/wiki/Self-excitation http://en.wikipedia.org/wiki/Self-excitation
- jacquesm 14y agoResidual flux is usually enough to start, but if you lose all flux for some reason (when the core is completely demagnetize) zapping it with DC can help restore it.