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Old 06-07-2012, 06:47 PM   #5162
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Joined: Sep 2009
Location: Melbourne, Australia
Oddometer: 2,071
Originally Posted by der_saeufer View Post
On a permanent magnet generator with an old-style shunt regulator (e.g. on a dirt bike or old UJM), does it even cause any extra engine load to run electrical accessories? I'm not an EE, but I thought the generator always ran full-bore and got rid of extra electricity as heat through the regulator vs. a car alternator where the magnetic field is actually stronger when the load is heavier.
These permanent magnet alternators are still very common and are not correctly termed generators because they produce an AC output (Alternator) which is then rectified and shunt regulated.

Using the term generator leads to misunderstandings like....

Originally Posted by bwalsh View Post
To you and the other inmate who mentioned generators...I was talking about vehicles from the eighties and nineties with alternators, not generators...
The only motorcycle I've ever owned in over 30 years of riding which doesn't have a permanent magnet alternator with a shunt regulator is a 1984 air cooled BMW boxer with an automotive style alternator with a field winding controlled by the voltage regulator. My near new outboard motor also has a 3 Amp permanent magnet alternator.

Field regulated alternators are still quite unusual on motorbikes.

Originally Posted by bwalsh View Post
The battery isn't going to be drained sitting at a stop light...hence the original remark.
If the lights are on, the lights are using energy.

That energy may be a trivial fraction of the engines output, or it may be power which the engine provides regardless of how it is used or not used (as is the case with the permanent magnet alternator or with a car heater which uses waste heat), but it has to come from somewhere.
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