[James_H._Harlow]_Electric_Power_Transformer_Engin(BookSee.org)

A six-pulse single-way transformer would have to have two secondary windings, like a Circuit 45
transformer (Figure 2.4.5), which has a delta primary winding with double-wye secondary windings. A
six-pulse double-way transformer can be a simple two-winding transformer, like a Circuit 23 transformer
(Figure 2.4.1), which is a simple delta-wye transformer. This is due to the number of pulses each circuit
has over the normal period of a sine wave.
31.
H 1
H 2
H
3
30¡
R 3
R 1 R 5
R 4
R 2
R 6
23.
H 2
R1
R
2
H
1
H
3
R
E 3
S
DELTA, TWELVE PHASE, MULTIPLE
DELTA-WYE, DOUBLE-WAY
FIGURE 2.4.4 ANSI Circuit 31. (From ANSI/IEEE C57.18.10-1998. © IEEE 1998. With permission.)
DELTA, SIX PHASE,
WYE, DOUBLE-WAY
45
H
2
N 1
N 0
N 2
R 3 R 2
FIGURE 2.4.1 ANSI Circuit 23. (From ANSI/IEEE C57.18.10-1998. © IEEE 1998. With permission.)
H
1
H
3
R 1
R 4
R 5
R 6
25.
H
2
H 1
H
3
30¡
R
E 2
S
R
R 3
1
DELTA, SIX PHASE, DOUBLE WYE
FIGURE 2.4.5 ANSI Circuit 45. (From ANSI/IEEE C57.18.10-1998. © IEEE 1998. With permission.)
46
N 0
N
H
R 1
N 2
2 3
R R
2
4
DELTA, SIX PHASE,
DELTA, DOUBLE-WAY
H 1 H
3
30¡
R 1
R
5
R
6
FIGURE 2.4.2 ANSI Circuit 25. (From ANSI/IEEE C57.18.10-1998. © IEEE 1998. With permission.)
26.
H 1
H2
H3
WYE, SIX PHASE,
DELTA, DOUBLE-WAY
FIGURE 2.4.3 ANSI Circuit 26. (From ANSI/IEEE C57.18.10-1998. © IEEE 1998. With permission.)
R 1
R 2
R 3
FIGURE 2.4.6 ANSI Circuit 45. (From ANSI/IEEE C57.18.10-1998. © IEEE 1998. With permission.)
2.4.4 Commutating Impedance
WYE, SIX PHASE, DOUBLE WYE
Commutating impedance is defined as one-half the total impedance in the commutating circuit expressed
in ohms referred to the total secondary winding. It is often expressed as percent impedance on a secondary
kVA base. For wye, star, and multiple-wye circuits, this is the same as derived in ohms on a phase-toneutral
voltage basis. With diametric and zigzag circuits, it must be expressed as one-half the total due
to both halves being mutually coupled on the same core leg or phase. This is not to be confused with
the short-circuit impedance, i.e., the impedance with all secondary windings shorted. Care must be taken
when expressing these values to be careful of the kVA base used in each. The commutating impedance
is the impedance with one secondary winding shorted, and it is usually expressed on its own kVA base,
although it can also be expressed on the primary kVA base if desired.
© 2004 by CRC Press LLC
© 2004 by CRC Press LLC