Open image in new window Fig. 14 Voltages across ZSBT and IPR when using the wye-connected autotransformer.
When using the wye-connected autotransformer, define the load power as P_{text{Y}} = U_{text{dY}} I_{text{dY}} (34).
2) Under the same load current, when using the delta-connected autotransformer, the input line current is greater than that of using the wye-connected autotransformer.
Therefore, the load power is about 10348.8 W. Open image in new window Fig. 12 Load voltage and load current of 12-pulse rectifier using the wye-connected autotransformer.
From (21), (22) and Fig. 6, when using the delta-connected autotransformer, the load voltage is greater than that of using the wye-connected autotransformer under the same input voltages.
6) Under the load power, when using delta-connected autotransformer, the kVA ratings of the ZSBT and IPR are equal to that of using the wye-connected autotransformer, respectively.
3) Because of the delta-connected autotransformer and wye-connected autotransformer operating under step-up and step-down condition, respectively, under the same input voltages, the load voltage when using the delta-connected autotransformer is greater than that of using the wye-connected autotransformer.
When using the wye-connected autotransformer, the RMS of the voltage across ZSBT is calculated as U_{{text{ZSBT}}{text{rm Y}} = sqrt {frac{8 - 3sqrt 3 }{2} - frac{9 - 3sqrt 3 }{pi }} frac{sqrt 3 }{ 2 (sqrt 3 + 1 )}U_{text{m}} (42).
From (13), (18), and Fig. 5, the following conclusions are obtained: 1) Under the same load current, when using the delta-connected autotransformer, the input line current is greater than that of using the wye-connected autotransformer, and the RMS ratio of the current i a∆ to current i aY is 4/3.
From (33), (45) and (47), when using the wye-connected autotransformer, the sum of the kVA rating of the magnetic devices is calculated as S_{{text{kVA}}{text{text{Y}}} = S_{{text{wye}}{text{rm con}{text{rm tran}} + S_{{text{ZSBT}}{text{text{Y}}} + S_{{text{IPR}}{text{text{Y}}} = 29.82% ;U_{text{dY}} I_{text{dY}} (49).
Under the same load current, when using the delta-connected autotransformer, the input line current is greater than that of using the wye-connected autotransformer, and the RMS ratio of the current i a∆ to current i aY is 4/3.
