Reference |
R-core Transformer |
Toroid Transformer |
EI Transformer |
Shape |
The Standard model is thin, small & light. |
Small transformer leads to higher
copper loss. |
The Ideal shape is square. The transformer
tends to be large & heavy. |
Leakage flux |
With
balanced winding canceling the leakage flux, the total
amount of leakage flux is extremely small. As a result
can be used even without shield. |
Winding is not balanced hence there
is lot of leakage flux. To reduce the effect there is
a need to provide shielding. |
There
are gaps in the magnetic path and the winding is not
balanced. As a result the leakage flux is very high
which can affect sensitive electronic components if
proper shielding is not provided. |
Winding |
Winding is done on special machine
resulting in evenly spaced winding. Balanced winding
is an inherent constituent of the design. |
The winding is not evenly spaced.
The density of turns on the inner edge is more and on
the outer edge the wires are roughly spaced out. Thus
the winding is not balanced. |
While
the layers of turns are well laid out the winding is
only on the center limb of the EI core. Thus it is not
balanced. |
Exiting Current
|
The exiting current is minimal as
all the magnetic paths are in alignment with the rolling
direction of the steel and there is no gap in the core. |
The exiting current is less than
that in EI Transformer, but the same is higher than
that of R-core transformer due to lack of balancing
of winding. |
More
exiting current is required due to presence of magnetic
gaps, the inability to use the effect of rolling direction
of grain oriented steel, the variation in assembly operation,
etc. |
Insulation |
Double structure bobbins are used
ensuring complete separation between primary & secondary
winding. Thus, safety standards are easily met. The dielectric
strength is more than adequate. |
The winding is done on the core without
the use of bobbin. Thus difficulties are observed in
meeting safety standards. |
Partition
bobbins allow separation between Primary and Secondary
bobbins but this is not complete. The dielectric strength
is not as good as R-core transformer. Difficulties are observed
in meeting safety standards. |
Efficiency |
Very low losses result in better
efficiency. Efficiency greater than 90% is generally
observed in most designs. |
Efficiency is better than EI transformer
but less compared to R-core transformer. |
More
losses result in poor efficiency. |
Heat |
Heat generation is minimal due to
low Iron loss. The large surface area of the coil allows
for better heat dissipation. |
The core is not exposed at any point.
Thus the heat generated has no area for dissipation.
Thus temperature rise is more. |
Due
to iron loss the heat generation is more. Further as
large part of the winding is covered inside the core
there is poor heat dissipation.
|
Mounting |
Due to the thin design & lightness
can be accommodated in available space of assembly.
Can also be mounted vertically on the sides. |
Because of circular shape the length
& width of the space should be identical. |
Usual
cubic space takes more space in assembly. |