Centrado transformers sell Auto / Insulation step up / step down transformer functions to increase and decrease voltage. Auto transformer with 1 roll, input / output one roll, 1ph / 3ph with input spec - 400 V and output spec: 200 - 220 V. Isolation of transformer with 2 input and output rolls separately, 1ph / 3ph with input spec - 400 V and output spec: 200-220 V. Winding: AL-AL / CU-CU, oil / dry type. With factory warranty.