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A simple power regulation circuit which converts 60Hz 120V 3-phase AC into regulated +12/-12v DC. What follows is a brief explanation of how it works.
The center tapped transformers fulfill two roles. First, they step down the 120VAC to 24VAC. Second, they output two phases that are offset by 60°, doubling the total number of phases fed to the rectification stage to 6, thus smoothing its output. Each phase transformer feeds its own bridge rectifier, which converts the power from 2 phase AC to +/- DC. A smoothing capacitor is also included to help reduce output ripple.
Following the rectification stage is the a power filter, which reduces the ripple from the rectifiers. These are passive LC band block filters tuned to block 360Hz, one for each polarity. Immediately following the filter, and preceding the regulator, are reservoir capacitors to absorb voltage fluctuations.
Next are active voltage regulators which utilize a transistor controlled by a zener diode to maintain a steady 12 volts, and whose operation is indicated by an LED (red for negative, and green for positive).
Finally, the actual load, a lamp, is at the bottom right. Throughout the circuit, meters have been placed at key locations. Given enough time, the meter at the load will indicate that the voltage has stabilized, indicating that the circuit is supplying essentially ripple-free 12V DC power.
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