Difference between Single-Phase Transformer and Three-Phase Transformer
The key differences between single phase and three phase transformers are highlighted in the following table
Parameter
Single-Phase Transformer
Three-Phase Transformer
Definition
A type of transformer which consists only
one pair of transformer windings (one
primary winding and one secondary winding)
and is used to step-up or step-down the single
phase alternating voltage is known as 'singlephase transformer'.
A transformer which has three pairs of transformer windings arranged in a
three-section iron core, where each section containing a pair of primary
and secondary windings, and is used for transforming the 3-phase
alternating voltage to the desired value is known as 'three-phase
transformer'.
Single-phase transformer has only one
primary winding and one secondary winding.
Three-phase transformer has three-primary windings and three secondary
windings.
Single-phase transformer has two input
terminals and two output terminals viz. phase
(P) and neutral (N).
In case of three-phase transformer, there are three input terminals for line
wires and one terminal is for neutral (depending upon the type of primary
winding connection), and similarly, at the output, three line terminals and
one neutral terminal be provided, again the presence of neutral terminal
depends upon the type of secondary winding connection.
The size of a single-phase transformer is
small.
A three-phase transformer is relatively larger in size.
Substitution
A single-phase transformer cannot be used
for supplying a three-phase load.
A three-phase transformer can be used to supply both 1-phase and 3-phase
loads.
Power handling
capacity
The power handling capacity of a singlephase transformer is less due to use of only
one set of windings.
A three-phase transformer can handle more power than a 1-phase
transformer.
There is only one primary winding and one
secondary winding, thus no specific winding
configuration exists in case of a single-phase
transformer.
Based on the connection of three primary windings and three secondary
windings, the following winding configurations are defined for the threephase transformerrs:
Number of
primary and
secondary
Input and
output
terminals
Size
Winding
configuration

Star-Start (Y-Y) Connection

Delta-Delta (Δ-Δ) Connection

Star-Delta (Y-Δ) Connection

Delta-Star (Δ-Y) Connection
Single-phase transformers are simple in
design.
The design of three-phase transformer is relatively complex due to
presence of three windings.
Efficiency
For same ratings, the efficiency of a singlephase transformer is less.
A three-phase transformer has high efficiency compared to 1-phase
transformer.
Capital cost
The initial cost of a single-phase transformer
is less.
The initial cost of a three-phase transformer is relatively higher than that
of 1-phase transformer.
Economical
The single-phase transformers are less
economical in long term.
The powerful and fast performance of the three-phase transformers make
them more economical over the long term.
Parallel operation of single-phase
transformers is difficult.
The parallel operation of three-phase transformers is easier than that of
the 1-phase transformers.
Single-phase transformers are used for small
loads such as to supply single-domestic loads
like pumps and lightings, etc., used in
various electronic devices like in TVs,
mobile chargers, etc. for voltage regulation,
in home inverters for stepping up voltage,
etc.
Three-phase transformers are used for supplying high power single-phase
as well as three-phase loads as induction motors, etc. Also used in power
systems for power transmission and distribution
Design
Parallel
operation
Applications