Electrical engineers

  W hat is an Autotransformer? An autotransformer (or auto transformer ) is a type of electrical transformer with only one winding. The “auto” prefix refers to the single coil acting alone (Greek for “self”) – not to any automatic mechanism. An auto transformer is similar to a two winding transformer but varies in the way the primary and secondary winding of the transformer are interrelated. Autotransformer Theory In an auto transformer, one single winding is used as primary winding as well as secondary winding. But in two windings transformer two different windings are used for primary and secondary purpose. A circuit diagram of auto transformer is shown below. The winding AB of total turns N 1 is considered as primary winding. This winding is tapped from point ′C′ and the portion BC is considered as secondary. Let’s assume the number of turns in between points ′B′ and ′C′ is N 2 . If V 1 voltage is applied across the winding i.e. in between ′A′ and ′C′. Hence, the voltage acro

D epending on the construction of its magnetic core, we can categorize transformers into two types: Shell Type Transformer Core Type Transformer Core of Shell Type Transformer We use ‘E’s and ‘L’s shape laminations to make the core of the shell-type transformer . Limb of Shell Type Transformer The core of a single phase shell type transformer is constructed with of three limbs (legs). This design increases the mechanical strength of the core. It also improves the protection of windings from external mechanical shocks. The HV and LV windings are wound around the central limb. The central limb carries the entire flux (φ), whereas the side limbs carry half of the flux (φ/2). Hence, to accommodate the flux the cross-section of the central limb is twice than that of the side limbs. The magnetic flux flows through two closed magnetic paths which decrease the core losses and hence increase the efficiency of transformer . So, shell type transformer gives more output compared to similar c

  Core Type Transformer:  What is it? There are two main types of transformers which can be categorized by the shape of the magnetic core. These are core type transformers, and shell-type transformers (and less commonly, air core transformers ). We shall discuss here the core type transformer . The core of single phase core type transformer is a single window core. This means there are two limbs as shown in the figure below. Both LV and HV windings are wrapped on both limbs. Normally both windings are divided into parts and one part of both windings are wrapped on one limb and other parts or halves are wrapped on the other limb of the core. The LV winding is first wrapped on the core limb surface with sufficient insulation between the core body and winding. Then the LV winding, HV winding is wrapped with sufficient insulation between LV winding and HV winding. In this way, both limbs are covered with LV then HV windings. This arrangement makes the transformer economical. Since the

Transformer is electromagnetic static electrical equipment (with no moving parts) which transforms magnetic energy to electrical energy. It consists of a magnetic iron core serving as a magnetic transformer part and transformer cooper winding serving as electrical part. The transformer is high-efficiency equipment, and its losses are very low because there isn’t any mechanical friction inside. Transformers are used in almost all electrical systems from low voltage up to the highest voltage level. It operates only with alternating current (AC), because the direct current (DC) does not create any electromagnetic induction. Depending on the electrical network where the transformer is installed, there are two transformer types, three-phase transformers and single phase transformers . The operation principle of the single-phase transformer is: the AC voltage source injects the AC current through the transformer primary winding. The AC current generates the alternating electromagnetic fie

Losses in Transformer As the electrical transformer is a static device, mechanical loss in transformer normally does not come into picture. We generally consider only electrical losses in transformer . Loss in any machine is broadly defined as difference between input power and output power. When input power is supplied to the primary of transformer , some portion of that power is used to compensate core losses in transformer i.e. Hysteresis loss in transformer and Eddy current loss in transformer core and some portion of the input power is lost as I 2 R loss and dissipated as heat in the primary and secondary windings, because these windings have some internal resistance in them. The first one is called core loss or iron loss in transformer and the later is known as ohmic loss or copper loss in transformer . Another loss occurs in transformer, known as Stray Loss, due to Stray fluxes link with the mechanical structure and winding conductors. Copper Loss in Transformer Copper loss