Quote:
Originally Posted by DannoXYZ
How can output voltage be zero when engine's spinning at 4000rpms? The magnets aren't adjustable like automotive alternators.
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Shunt regulators either let all the output through, or momentarily short it all to ground, many times per second. When current is not needed the regulator simply shorts the alternator output to ground, taking its output voltage to zero. Current is limited because of the fixed field strength of the permanent magnets, so it doesn't suffer from any unusually high current from the short circuit.
This all or nothing approach is why a shunt regulator doesn't have to dissipate huge amounts of power. Note that the input to the regulator (alternator output) is what's shunted to ground, not the regulator output, which sits at battery voltage!