This document discusses different wiring configurations for connecting multiple transformers together. It describes Y-Y, Y-Δ, Δ-Y, and Δ-Δ configurations, showing diagrams of how the transformer windings are connected in each case. It notes that a Δ-Δ configuration is preferred when there is no need for a neutral conductor in the secondary system, and also describes an "open Δ" or "V" configuration using only two transformers instead of three.

1. this phasing correct when the windings aren’t shown in regular Y or ∆
tricky. Let me illustrate, starting with Figure 10.42.
A1
B1
C1
T1 T2 T3
A2
B2
C2
42: Inputs A1 , A2 , A3 may be wired either “∆” or “Y”, as may outputs B1
dividual transformers are to be connected together to transform powe

2. Y-Y
A1
1º B1
C1
N1
T1 T2 T3
N2
A2
2º B
2
C2
A -A B-B C-C

5. Y-!
A1
B1
C1
N1
T1 T2 T3
A2
B2
C2
Figure 10.44: Phase wiring for “Y-∆” transformer.

7. Y-!
A1
B1
C1
N1
T1 T2 T3
A2
B2
C2
Figure 10.44: Phase wiring for “Y-∆” transformer.

8. !-Y
A1
B1
C1
T1 T2 T3
N2
A2
B2
C2
Figure 10.45: Phase wiring for “∆-Y” transformer.
Such a configuration (Figure 10.45) would allow for the provision of multiple voltages (line-
to-line or line-to-neutral) in the second power system, from a source power system having no
neutral. “STAR”
And finally, we turn to the ∆-∆ configuration: (Figure 10.46)
When there is no need for a neutral conductor in the secondary power system, ∆-∆ connec-
tion schemes (Figure 10.46) are preferred because of the inherent reliability of the ∆ configu-
ration.
Considering that a ∆ configuration can operate satisfactorily missing one winding, some
power system designers choose to create a three-phase transformer bank with only two trans-
formers, representing a ∆-∆ configuration with a missing winding in both the primary and
secondary sides: (Figure 10.47)
This configuration is called “V” or “Open-∆.” Of course, each of the two transformers have
to be oversized to handle the same amount of power as three in a standard ∆ configuration,

10. !-!
A1
B1
C1
T1 T2 T3
A2
B2
C2
Figure 10.46: Phase wiring for “∆-∆” transformer.
"Open !"
A1
B1
C1