A historic rotating machine that acts as both a motor and a generator in a single armature. It runs on alternating current to spin the rotor, while a commutator on the same shaft physically rectifies the power to output direct current. These massive machines were standard in early railway and industrial substations before solid-state electronics existed.
The old traction substation still has the concrete pads where the rotary converters sat.
You will only see these in museums or historic documents. They were entirely replaced by mercury-arc rectifiers and later by silicon diodes.
Related terms
Commutate
To reverse the direction of electric current in a specific winding or circuit branch.
Mercury arc rectifier
A historic glass or steel vacuum tube device used to convert high-voltage alternating current into direct current.
Dynamo
An electrical generator that produces direct current using a commutator.