1.1. principal of operation
Transformer operate relies on the principle that electricity is transferred expeditiously by magnetic induction from one circuit to another circuit. One winding of a electrical device is energized from electricity (AC) supply, alternating force field is established within the electrical device core. Alternating magnetic lines of force, referred to as “flux” flow in to through the core. With a second winding round the same core, a voltage is induced by the alternating flux lines. A circuit, connected to the terminals of the second winding, leads to current flow.
Each section of electrical device consists of two separate coil winding wound on a typical core. The low tension winding is placed nearest the core, the high voltage winding is then placed around each the low voltage winding and core. See figure internal construction of one phase. The core is usually made of terribly skinny steel lamination, every coated with insulation, by insulating between individual laminations, losses are reduce. The steel core provided a winding square measure insulated from the core and from one another and lead square measure brought out through insulating bushings.
A three-phase transformer typically has a core with three legs and has both high voltage and low-voltage windings around each leg. Special paper and wood are used for insulation and internal structural support.
1.2. Transformer action
Transformer action depend upon magnetic lines of force (flux) mentioned higher than at the moment a electrical device primary is energized with AC ,a flow of electrons (current) begins. Through out the positive portion of the wave, lines of magnetism (flux) develop outward from the coil and still expand till this is it its positive peak. The force field is additionally at its positive peak. This wave then begins to decrease, crosses zero, and goes negative till it reaches its negative peak. The magnetic flux switches direction and additionally reaches its peak within the opposite direction. With ac power circuit, this changes regularly sixty times per different frequency. In Europe, fifty cycles per second is common. Strength of a force field depends on the quantity of current and number of turn within the winding. Once current is reduced, the force field shrinks. Once this is transitioned, the force field collapses.
When a coil is placed in AC circuit, as shown in figure. Current within the primary are in the course of a perpetually rising and collapsing force field. Once another coil is placed at interval the alternating force field of the primary coil, the rising and collapsing flux can induce voltage within the coil can cause a current within the second coil. The coils square measure aforesaid to be magnetically couple they are however, electrically isolated from one another.
Many transformers have separate coil, as shown in figure 3. And contain several turns of wire and a core that form a path for and concentrates the magnetic flux. The winding receiving electricity from the supply is termed the first winding. The winding that receives energy from the first winding, via the force field, is termed secondary winding .
Either the high- or low tension winding are often the first or the secondary. With GSUs at reclamation power plant, the fist winding is that the low tension aspect and therefore the high voltage aspect is that the secondary coil. Where power is employed, the fist winding is that the high voltage aspect, and therefore the secondary coil is that the low tension aspect
The amount of voltage induced in every flip of the secondary coil are identical because the voltage across every flip of the winding. The full quantity of voltage induces in every flip. Therefore, if the secondary, and therefore the electrical device is known as a step-up transformer. If the secondary coil has fever turns than the fist, a lower voltage are induced within the secondary; and therefore the electrical is a step-down transformer. Note that the first is often connected to the supply of power, and therefore the secondary is often connected to the load.
In actual observe, the quantity of power on the market from secondary will be slightly but the quantity equipped to the fist due to losses within the electrical device itself.
When an in AC generator is connected to the first coil of a transformer fig 4, electrons flow through the coil because of the generator voltage. Electricity varies, and attendant magnetic flux varies, cutting each electrical device coil and inducement voltage in every coil circuit.
The voltage induce within the primary opposes the applied voltage and is understood as back voltage or back electro motive force. Once the secondary circuit is open, back EMF, alongside the primary circuit resistance, acts to limit the first current. Primary current should be spare to keep up enough force field to produce the specified back EMF.
When the secondary circuit is closed and a load is applied, current appears within the secondary because of induced voltage, ensuing from flux created by the first current. This secondary current sets up a second force field within the electrical device within the other way of the primary field. Thus the two fields oppose one another end in a combined force field of less strength than the one field produced by the first with the secondary open. These reduce the back voltage of the first and cause the first current to extend. The first current will increase till it re-establishes the total force field at its original strength.