Electrical Machine - IES Academy
Electrical Machine - IES Academy
Electrical Machine - IES Academy
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India’s No. 1<br />
<strong>IES</strong> <strong>Academy</strong><br />
Transformer<br />
Chapter-1<br />
The phasor diagram is shown from which it is easily seen that the voltage of the corresponding<br />
phases (and therefore of the corresponding lines) are in phase. This is known as the 0°connection.<br />
The letters within brackets on the phasor diagram indicate the lines, to which the<br />
terminals are connected. If the winding terminals on secondary side are reversed, the 180°connection<br />
is obtained.<br />
Phase transformation ratio → x : 1<br />
Line transformation ratio → x : 1<br />
Delta/Delta (Dd) Connection – (0° and 180° connections<br />
are obtained)<br />
Figure shows the delta/delta connection and the corresponding phasor diagram. The sum of<br />
voltages around the secondary delta must be zero; otherwise delta, being a closed circuit,<br />
means a short circuit. With polarities indicated on the primary and secondary sides, voltages<br />
Va2a1, Vb2b1 and Vc2c1 add to zero as per the phasor diagram if the delta is formed by connecting<br />
a1b2, b1c2 and c1a2. It is easily seen from the phasor diagram that the primary and secondary<br />
line voltages are in phase so I t is the 0°-connection. However, if the secondary leads a, b, c are<br />
taken out from the delta nodes a1b2, b1c2, c1,c2, the secondary voltages are n phase opposition to<br />
the primary voltage. This is the 180°-connection.<br />
Phase transformation ratio → x : 1<br />
Line transformation ratio → x : 1<br />
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