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DIY Generator Voltage Regulator

David Sandoval

Electric power generators are used for powering electrical and electronic devices when no other appropriate power source is readily available. Generators convert mechanical energy into electrical energy. The device (such as a gasoline engine) providing the mechanical power to a generator is often prone to underspeed or overspeed conditions, which often create power surges and "sags."

To minimize the danger of such conditions, a voltage regulator circuit may be attached to the generator output connection.

How a Generator Works

Gasoline and diesel engines are commonly used in generators.

A generator is essentially an AC motor used in reverse. Instead of using electrical energy to create mechanical energy, the operating principle of a generator is that the generator uses mechanical energy to create electrical energy in an alternating current form.

Because alternating electrical current magnitude is always changing, AC electrical energy cannot be stored as AC energy, nor can it be directly voltage-regulated like DC electrical energy can. Instead, AC electrical energy must be converted to DC (direct current) electrical energy before it can be stored.

AC to DC Conversion

For practical purposes, AC electrical energy can be regulated by converting to DC electrical energy, using a storage device such as a battery to store the converted energy, and inverted back into AC electrical energy.

Most generators for sale to the public provide AC electrical energy at a voltage level similar to what is available from a wall outlet. The first step in converting AC electrical energy to DC electrical energy would be to convert the AC signal from a household voltage (110-120 VAC) into a smaller voltage that can be used to charge a battery (such as 12 VAC). Use a step-down transformer to reduce the voltage. Connect the side with more windings to the higher voltage power supply.

The next step in converting AC electrical energy to DC is rectifying the smaller voltage AC signal. The easiest way to accomplish this is to use a rectifier diode pack. Connect one of the transformer leads on the side with fewer windings to one of the "AC" terminals on the rectifier diode pack. Connect the other transformer lead to the remaining "AC" terminal on the diode pack. Connect the rectifier "+" terminal to the positive terminal on the battery. Connect the rectifier "-" terminal to the negative terminal on the battery.

In this circuit, the battery serves as a filter, absorbing any surges or spikes in power and providing a consistent power source even if the generator fails.

DC to AC Inversion

To operate equipment designed for AC electrical power, regulated DC electrical energy must be inverted back into AC electrical energy. A special electronic device called a power inverter is used for this purpose.

Choose a power inverter that provides the necessary power for your needs. Calculate how much electrical power is needed by multiplying voltage times current (in amps) to determine how much power (in watts) is needed.

If more than 400 watts of power are needed from the regulated power supply circuit, choose a power inverter that can be hardwired to the battery. This will allow the power inverter to draw the necessary electrical current to supply your needs.