Question:  What is a Voltage Regulator and how does it work?

Answer:  The short answer is a voltage regulator automatically regulates voltage with the net result being a constant voltage level.

However, the good answer is far more complicated.  Back when generators were first being used in the early nineteen-twenties, there used to be a man standing at a control panel in front of a wheel (much like the one pictured here) and his task for his entire shift was to watch the voltmeter, then adjust the wheel (which varied the DC voltage to the rotor) to maintain a steady output relative to the load.  This voltage regulation method, though simple, if used today would prove woefully uneconomical and unstable.

Voltage Adjust Wheel

However, as simple as that method was, it is exactly (and basically) the way regulators work today, minus (of course) the very bored man at the adjust wheel.

Technically, it works like this; As electrical power (watts) is applied, voltage tends to drop. When voltage drops below its predetermined value, the regulator applies more DC current to the field and the output AC voltage rises. When the voltage rises above its predetermined value, the regulator reduces the DC voltage supply to the field and the AC voltage falls. The constant checking and comparing of the voltage through a sensing circuit is how the voltage regulator controls the field current applied to the spinning rotor inside the alternator. The resulting product is a constant regulated AC voltage.

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