Anyone who’s ever turned on a computer knows that electronics can be sensitive. As electronics go, those installed in aircraft are subjected to some of the harshest environments on Earth. Pressure, vibration, and temperature change are but a few of the many hazards.
The aircraft’s main power source, the alternator, is in effect, dumb. It simply turns mechanical energy from the engine into electrical energy through an electromagnet called a rotor. What makes the entire system work is a solid-state device bolted inside the cowling in line between the alternator and the electrical buses called a voltage regulator.
The regulator is set to maintain a specific system voltage. In a 12- volt system, it’s usually about 14.2 volts. The electrical system can be thought of in terms of water pipes where voltage is the water pressure. As something on the panel is turned on, it’s as if a valve is opened on a pipe, thereby decreasing the overall pressure. When this happens, the electrical bus sends a signal to the voltage regulator to increase the voltage through pulse width modulation (Google that one). From here, the regulator goes to work essentially turning on and off a switch that tells the alternator to produce power. The more power that’s needed for the bus, the longer the “on” period of the signal. The circle is complete because the alternator often is wired directly to the bus, giving the necessary power. All this happens almost instantly, many times a second.
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