Parallel OPerations of single phase Transformers

1. PARALLEL
OPERATION OF
SINGLE PHASE
TRANSFORMER
Lecture Notes by Dr.R.M.Larik 1

2. INTRODUCTION
➢ The transformers are connected in parallel when load on one of the
transformers is more than its capacity.
➢ Two transformers are said to be connected in parallel if the primary
windings are connected to supply busbars and secondary windings
are connected to load busbars.
➢ The reliability is increased with parallel operation than to have
single larger unit.
➢ The cost associated with maintaining the spares is less when two
transformers are connected in parallel.
Lecture Notes by Dr.R.M.Larik 2

3. Conditions for Parallel Operation
Lecture Notes by Dr.R.M.Larik 3

4. CONDITION (I)
Lecture Notes by Dr.R.M.Larik 4

5. CONDITION (II)
Lecture Notes by Dr.R.M.Larik 5

6. Lecture Notes by Dr.R.M.Larik 6

7. CONDITION (III)
Lecture Notes by Dr.R.M.Larik 7

8. CONDITION(IV)
➢If the reactance/resistance ratios of the two
transformers are not equal, the power factor of the load
supplied by the transformers will not be equal.
➢In other words, one transformer will be operating with
a higher and the other with a lower power factor than
that of the load.
Lecture Notes by Dr.R.M.Larik 8