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UNIT-III
Transformers
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INTRODUCTION
Transformer is a static device which transfers electrical energy from one electrical circuit to
another electrical circuit without change in frequency through magnetic medium. The winding which
receives energy is called primary winding and the winding which delivers energy to the load is called
secondary winding.
Based on the voltage levels transformers are classified into two types
i. Step down transformer ii. Step up transformer.
CONSTRUCTION
CORE-TYPE AND SHELL-TYPE CONSTRUCTION
Depending upon the manner in which the primary and secondary windings are placed on the core, and
the shape of the core, there are two types of transformers, called (a) core type, and (b) shell type. In core
type transformers, the windings are placed in the form of concentric cylindrical coils placed around the
vertical limbs of the core. The low-voltage (LV) as well as the high-voltage (HV) winding are made in
two halves, and placed on the two limbs of core. The LV winding is placed next to the core for economy
in insulation cost. Figure a shows the cross-section of the arrangement. In the shell type transformer, the
primary and secondary windings are wound over the central limb of a three-limb core as shown in Figure
b. The HV and LV windings are split into a number of sections, and the sections are interleaved or
Φ
sandwiched i.e. the sections of the HV and LV windings are placed alternately.
H.V. winding
φ
Core
φ
LV
Φ
Limb
or leg Gaps
HV
LV
HV
L.V. Winding
(a) core type (b) Shell Type
CORE
The core is built-up of thin steel laminations insulated from each other. This helps in reducing the eddy current
losses in the core, and also helps in construction of the transformer. The steel used for core is of high silicon content,
sometimes heat treated to produce a high permeability and low hysteresis loss. The material commonly used for core
jntuworldupdates.org Specworld.in
UNIT-III
Transformers
jntuworldupdates.org Specworld.in
, Smartzworld.com Smartworld.asia
INTRODUCTION
Transformer is a static device which transfers electrical energy from one electrical circuit to
another electrical circuit without change in frequency through magnetic medium. The winding which
receives energy is called primary winding and the winding which delivers energy to the load is called
secondary winding.
Based on the voltage levels transformers are classified into two types
i. Step down transformer ii. Step up transformer.
CONSTRUCTION
CORE-TYPE AND SHELL-TYPE CONSTRUCTION
Depending upon the manner in which the primary and secondary windings are placed on the core, and
the shape of the core, there are two types of transformers, called (a) core type, and (b) shell type. In core
type transformers, the windings are placed in the form of concentric cylindrical coils placed around the
vertical limbs of the core. The low-voltage (LV) as well as the high-voltage (HV) winding are made in
two halves, and placed on the two limbs of core. The LV winding is placed next to the core for economy
in insulation cost. Figure a shows the cross-section of the arrangement. In the shell type transformer, the
primary and secondary windings are wound over the central limb of a three-limb core as shown in Figure
b. The HV and LV windings are split into a number of sections, and the sections are interleaved or
Φ
sandwiched i.e. the sections of the HV and LV windings are placed alternately.
H.V. winding
φ
Core
φ
LV
Φ
Limb
or leg Gaps
HV
LV
HV
L.V. Winding
(a) core type (b) Shell Type
CORE
The core is built-up of thin steel laminations insulated from each other. This helps in reducing the eddy current
losses in the core, and also helps in construction of the transformer. The steel used for core is of high silicon content,
sometimes heat treated to produce a high permeability and low hysteresis loss. The material commonly used for core
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