Raytech mini-ATOS Instruction Manual page 12

voltage written on the nameplate is 230V which consists of 500 turns from manufacturing data. The
following equations are valid:
With three-phase transformers of different configurations, turns ratio and voltage ratio can be
different.
Figure 3: Three-phase transformer schematic with Dyn11 vector group
For example, Figure 3 shows a three-phase transformer schematic with a delta connection on the
primary and star connection on the secondary side. 120000V and 20000V are written as primary
and secondary rated voltages respectively on the nameplate. The rated values are always line-line
voltages and the voltage ratio can simply calculate as follow:
Here, turns ratio is different from the voltage ratio because the low voltage side connection is star
and line-line rated voltage is different from the phase voltage. So, a factor of √ 3 is required as
follow to calculated the nominal turns ratio:
When we know the number of turns from the manufacturing data, the turns ratio can be calculated
directly. Consider that for the current example the number of turns is 93531and 9000 for each
primary and secondary winding respectively. The following equations are valid:
���������� ���������� =
90297-0.24 Instruction Manual mini-ATOS
���������� �������������� ��������������
�������������� ���������� =
���������� �������������� ������������������
�������������� ������������ ���� ����������
���������� ���������� =
������������������ ������������ ���� ����������
�������������� ���������� = ���������� ���������� = 30
���������� �������������� ��������������
�������������� ���������� =
���������� �������������� ������������������
���������� ���������� = �������������� ���������� × √3 = 6 × √3 = 10.3923
�������������� ������������ ���� ����������
������������������ ������������ ���� ����������
Preliminary
6900
= = 30
230
15000
= = 30
500
120000
= = 6
20000
93531
= = 10.3923
9000
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