Carroll & Meynell 3 phase transformers(enclosed) provide a trouble free and efficient way of varying and controlling AC voltages. Variation of the output voltage is achieved by a rotating arm and a carbon brush that rolls around a winding commutator.
These 3 phase variable autotransformers consist of three single phase variacs that are mounted on a common shaft and connected in the “star” vector configuration. The variacs are positioned so that the brush arms on each unit are matched.
This new range of autotransformers uses round carbon brushes, riding out any imperfection which gives a smoother operation. The round Carbon brush should last the lifetime of the unit.

High Efficiency. No Waveform Distortion. Excellent Regulation
Centre tap in winding for buck-boost applications
Rugged Construction. Low Operating Torque. Smooth and Linear Output
Low current density in round carbon brush. Low Magnetising Current.

Variable Auto Transformers

Continuously variable alternating current (a.c.) output voltage
Rugged construction
Low operating torque
High efficiency/excellent regulation

Silver-plated commutator
Low magnetising current
No waveform distortion, smooth linear output & overload capacity
Screw terminals
Complete with knob and dial