New Autotransformer 6 kVA * Three Phase * Primary: 600 Volt * Secondary: 400 Volt Conductor: Copper. Three phase Autotransformer RC6J-G1 has common primary-secondary windings which are not insulated from each other, offers no interference or disturbance isolation between primary and secondary circuits. It is an economical solution but is not suitable for sensitive equipment with electronic components and perfectly suitable for simple motor and heater applications.