The device, whose scheme is shown in the figure can be used to adjust the voltage at the load active and inductive in nature, powered by AC voltage 127 and 220 V. the voltage at the load can be changed from zero to the nominal supply voltage.
The thyristor D5 included in the diagonal bridge composed of diodes D1-D4 plays the role of the managed key which opens when the discharge of the capacitor C1 through restrictive resistor R2 and managing the transition of the thyristor when you turn on the switching diode D6. The voltage at which the thyristor turns on, can be adjusted the potentiometer R1. Instead of the switching diode D6 can be used Zener diode, but in this case decreases the range of voltage adjustment at the load.
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