Types of Transformer Windings and Insulations

2. Transformers can be classified
based upon the core construction or
the shape of the magnetic core.
Core Type Transformers
Shell Type Transformers

3. • In core type we wrap the
primary and secondary
windings on the outer
limbs
• In Shell Type
Transformers the primary
and secondary windings on
inner limbs.

5.  Core Type Transformers use concentric
type windings
 In concentric windings low voltage
windings are placed near the core
Why Concentric Windings?
Because they help to reduce the leakage
reactance to a small value.

7. Windings are further classified into the
following types
Core Type Transformer Shell Type Transformer
Cylindrical Windings Sandwich Type Winding
Helical Windings
Single Helical Windings
Double Helical Windings
Disc-Helical Windings
Crossover Windings
Continuous Disc Windings

8. Typical Features of the Cylindrical
Winding include:
 Layered – Single or Multi-layered
 Use a rectangular or round Conductor
 Wound either on the flat side or on the
edge side

11.  Rectangular Strips wound in the form of a
Helix.
 The maximum number of strips used in
parallel to make up a conductor is 16.
 Helical Windings are further classified
into:
 Single Helical Winding
 Double Helical Winding
 Disc-Helical Winding

14. The conductors are paper covered round
wires or strips.
The windings are divided into a number of
coils in order to reduce the voltage between
adjacent layers.
These coils are axially separated by a distance
of 0.5 to 1 mm.
The width of the coil is 25 to 50 mm.
Mechanical Strength: Crossover Winding>Cylindrical
Winding
Impulse Strength: Cylindrical Winding>Crossover
Winding

16.  Flat Coils or discs (4-5) in series.
 For its robust construction, the
conductors can be a single strip or
multiple strips in a parallel wound on
the flat side.
 Discs are separated from each other
with press-board sectors attached to
vertical stripes.

19. Where several parallel conductors are
used, they are continuously transposed to
minimize circulating currents and
receive the same magnitude of induced
voltage.

20.  Transformer windings are exposed to
transient over-voltages like
 Switching surges,
 Lightning surges
 Chopped –Wave Impulse

22.  These are used in shell type transformer
 High Voltage and low voltage windings are
divided or split into a number of sections
 Leakage reactance can be easily controlled.
 The nearer two coils are on the same
magnetic axis, the greater is the proportion
of mutual flux and the less is the leakage
flux.

24. Insulation is provided between
LV and Core
HV and LV Winding
HV Winding and Core
Turn-to-Turn
Kraft Paper/Pressboard is used to insulate
every inch of copper.

25. Type of Winding Configuration Application
Cylindrical
Windings
Rectangular Used for low voltage
windings up to 6.6 KV
and 600-750 KVA
Circular Used for HV windings
with rating 6.6,11, and
33 KV
Helical Windings
Used as LV coils for
medium and high
capacity transformers
with I rating as high as
2000 A. (LV voltage and
High I ratings)

26. Type of Winding Configuration Applications
Crossover Windings
 Suitable for I rating not
exceeding 25 A
 Used as a HV winding for
small transformers
Interleaved Disc
Windings
 Used to reduce impulse surge
voltages
Continuous Disc
Winding
 Used as both HV and LV
windings in large capacity
transformers.
 Usually used for I and V
rating between 12-600 A
medium I ) and 33KV to
132 KV.

27.  Types of Transformer Core

28.  Types of Winding

29. Thank You