File:PЧГ-31T Carbon Pile Voltage Regulator side view.jpg

English: PЧГ-31T Carbon Pile Voltage Regulator

Made in the former Soviet Union, 1970s.

This carbon pile voltage regulator has been used on small general aviation (GA) aircraft to maintain constant generator voltage under the varying loads and speeds encountered. The speed requirement is especially severe as aircraft generators are driven from the main engines and thus are subjected to a speed range of at least two to one. The carbon voltage regulator consists of a carbon column, placed in a ceramic tube, fixed in a ribbed radiator casing, an electromagnet with a core and a movable armature, mounted on a spring steel lamellar plates and an adjusting screws. A winding is located on the core of the electromagnet.

A Carbon Pile Voltage Regulator uses a stack of pure carbon discs for the variable resistance element. A spring holds pressure on the stack to reduce its resistance when the generator output voltage is low. This allows maximum field current to flow. The field from an electromagnet, whose strength varies directly with the generator voltage, opposes the spring to loosen the stack and increase its resistance when the generator voltage needs to be decreased. The increased resistance decreases the field current and reduces the output voltage.