How to design a three-phase autotransformer?

The schematic diagram of a three-phase step-down autotransformer with Y-connection is shown in the figure.

1. Calculation of the capacity of an autotransformer

Transmission capacity

Self-capacity

2. Voltage per turn calculation

et: Voltage per turn, V/turn

3. Selection of core area

S: Cross-sectional area of ​​the iron core, in square centimeters.

4. Calculation of the number of turns in the winding

Primary winding (excluding common winding):

5. Capacity calculation per phase

6. Phase voltage calculation

Primary phase voltage(V):

Secondary phase voltage(V):

7. Current Calculation

Primary current:

Secondary current:

8. Calculation of conductor cross-sectional area

Primary insulated wire:q1=I1/j

Secondary insulated wire:q2=I2/j

Common winding insulation wire:q=I/j