different connection of three phase transformer with advantages and disadvantages, tertiary winding

1. Content:
 Introduction to three phase transformer.
 Advantages and disadvantages of single phase transformer.
 Different types of 3 phase transformer connection.
 Advantages and disadvantages of three phase transformer.
 Tertiary windings
 References
S.RAGUL,
ASSISTANT PROFESSOR,
DEPARTMENT OF EEE,
KNCET
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THREE PHASE TRANSFORMER KONGUNADU COLLEGE OF ENGINEERING & TECHNOLOGY

2. INTRODUCTION
A three-phase transformer can be obtained in two
different ways.
 Three numbers of identical single-phase transformers
can be suitably connected to make a three-phase
transformer. Such three-phase transformers are called
a bank of three-phase transformer.
 Alternatively, a three-phase transformer can be
constructed as a single unit.
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3. ADVANTAGES OF SINGLE UNIT
THREE-PHASE TRANSFORMER
1. It occupies less space
2. Its weight is less
3. Its cost is comparatively less
4. It is much easier to transport
5. It is more efficient
6. Core size is comparatively small.
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4. DISADVANTAGES OF SINGLE UNIT
THREE-PHASE TRANSFORMER
 When one of the phases of a single-unit three-phase
transformer becomes faulty, the entire unit of three-
phase transformer needs to be removed from the
supply for repair.
 But in the case of a bank of three-phase transformer,
only the faulty transformer is removed from the supply
for repair while the other two transformers remain
connected in the system without interrupting the
supply completely.
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5. CONSTRUCTION
Core type Shell type
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6. Star–Star (Υ–Υ) Connection of
Three-phase Transformer
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7. Delta–Delta (Δ–Δ) Connection of
Three-phase Transformer
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8. Delta–Star (Δ –Υ) Connection of
Three-phase Transformer
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9. Star–Delta (Υ–Δ) Connection of
Three-phase Transformer
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10. Open Delta (V–V) Connection of Three-
phase Transformer
Some of the features of open delta connection are
• The power handling capacity of open delta circuit is 0.577 times that of
delta–delta circuit.
• The secondary terminal voltage becomes unbalanced with increase in
load.
• The power factor is 86.6% of the balanced load factor.
• The two transformers in open delta connection will be operated at
different power factor.
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11. Scott (T–T) Connection of Transformer
It is a type of circuit used to derive two-phase electric power
from a three-phase source, or vice-versa. The Scott connection
evenly distributes a balanced load between the phases of the
source.
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12. CONVERSION FROM THREE-PHASE
TO TWO-PHASE
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13. Double Star Connection
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14. Double Delta Connection
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15. Six-phase Star Connection
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16. Diametric Connection
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17. Advantages of using tertiary
winding in transformer
i) This transformer has the ability to redistribute the flow
of fault current
ii) It reduces the unbalancing in the primary due to
unbalancing in three-phase load.
iii) Auxiliary load at different voltage levels from the
tertiary winding can be supplied from this transformer in
addition to its main secondary load.
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Conclusion:
 The Advantages and disadvantages of single phase transformer, different
types of 3 phase transformer connection, advantages and disadvantages of
three phase transformer and Tertiary windings is explained in detail with
suitable diagrams.
References: