Hey there well i just wanna to know how does a AVR (automatic voltage regulator) works in a alternator. does anyone know? cheerz
by 
heyzus
ANSWERS: 1
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It works by monitoring the alternator output voltage, and then varying the average current in the field/stator windings to maintain a constant output voltage, even when the load changes dramatically. The engine turns the rotor in the alternator, and the rotor windings rotate in a magnetic field generated by the stator winding. The stronger the stator field, the more current is induced in the rotor winding, and the greater the output current/voltage. So if the voltage rises too high, because you've switched off the aircon, the AVR reduces the field current and the alternator output drops, even if the engine is still running at the same speed. To avoid excess heat dissipation, the regulator operates in pulse mode, and actually varies the on/off ratio to produce an average current - you can observe this with a portable oscilloscope as you switch on the headlights whilst idling. The circuit inside is often on a ceramic hybrid PCB, and looks simple, but contains clever thermal compensation amongst other things. I missed this when I built my own replacement, and boiled my battery after 20 miles! D'oh..
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