Quote:
Originally Posted by Varn
Motorcycles have used permanent magnet alternators for some time. The trouble with them is that they have to shunt excess energy to ground. Not as efficient way of making power as one would think. ..
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(Motorcycle) PM generators are efficient,
1. no field charge, ever
2. no fan needed
3. excess current is not "shunted to ground", that would only make the engine do extra work.
Newer units *should* be utilizing switching(pwm) to ensure only enough energy is tapped from the alternator to maintain battery voltage. Older units probably used linear regulation which makes more heat, which may be the source of the confusion. If the regulator designers are really geeky they would add synchronous rectification, which has far less loss than plain old bridge rectification. But we are not talking about a huge amount of current on your typical motorcycle and it adds significantly to the cost vs a simple pwm scheme and a handful of diodes.