The column core is similar to the general transformer, and it is made of silicon steel. The ring core is rolled with a silicon steel strip. 20kVA and the following small capacity self-coupling voltage regulator, more choose ring type iron core; More than 20kVA users adopt column core. In the structure of the ring-type auto voltage regulator, the winding is wrapped in a single layer of insulated copper wire around the ring core. If the current capacity is greater than 10A, it can be used in parallel with two or more brushes. The self-coupling voltage regulator is generally made from cold and dry. Oil immersion is also used in special occasions with large capacity or special circumstances. Three ring - type single - phase self - coupling voltage regulator can be composed of three - phase self - coupling voltage regulator. The three-phase self-coupling voltage regulator is essentially a self-coupling transformer with continuous voltage regulation. There are two types of core - ring and column. The surface of the coil is polished to a smooth surface, and the brush with the electrochemical graphite is in contact with it. The brush can be used to rotate the surface of the wire to change the output voltage. 

Ltekonline are the manufacturers of Three Phases Induction Voltage Regulator used to demonstrate engineering principles in Engineering Colleges, Engineering Schools and Electrical Training Equipment Products for Engineering Teaching Lab in Universities