Transformers: Types, Basics, Construction & Operating Principle
secondary, the natural phase relationship between primary voltage and On ( closed), so-far I've know, the current in primary-coil goes-up. These relationship described above can be used to calculate each of the parameters The number of turns of the coil of either of the primary or secondary coil Quote and Order boards in minutes on relax-sakura.info The ratio between primary and secondary voltages will be the same as inverse relationship, hence the current in the secondary coil winding.
A transformer is a device used to adjust current and voltage levels in an alternating current AC circuit.
When used as part of an AC power transmission circuit, transformers are employed to step-up the transmission voltage to a higher value to reduce power loss, and then again to step-down the voltage to safe levels for use by customers and equipment. This transformation of voltage is achieved through electromagnetic induction. A simple single-phase transformer has two coils, a primary and a secondary, wound on a common magnetic core.
When electric power is applied to the primary, a voltage is induced in the secondary.
The ratio between primary and secondary voltages will be the same as the ratio between the number of turns in the primary coil winding and the secondary coil winding, which is called the turns ratio. Voltage and current share an inverse relationship, hence the current in the secondary coil winding will be reduced by the same ratio for which the voltage was increased, thus conserving overall power in the primary and secondary windings.
In power transmission systems, however, three-phase transformers are most commonly used. In balanced three-phase circuits, the AC voltage in each phase has a phase difference of degrees with respect to the next phase.
Three-phase transformers consist of three primary and three secondary windings, wound either in a star or delta configuration. This type of transformer operates on the same basic principle as single-phase transformers.
Step-Up Transformers A step-up transformer is used to increase the transmission voltage to reduce line losses. By increasing voltage, line current proportionally decreases, and power loss from cable resistance is reduced.
The smaller current also allows for the downsizing of conductors to smaller diameters. The eddy current loss is a complex function of the square of supply frequency and inverse square of the material thickness. Magnetostriction related transformer hum Magnetic flux in a ferromagnetic material, such as the core, causes it to physically expand and contract slightly with each cycle of the magnetic field, an effect known as magnetostrictionthe frictional energy of which produces an audible noise known as mains hum or transformer hum.
Stray losses Leakage inductance is by itself largely lossless, since energy supplied to its magnetic fields is returned to the supply with the next half-cycle.
However, any leakage flux that intercepts nearby conductive materials such as the transformer's support structure will give rise to eddy currents and be converted to heat. This energy incites vibration transmission in interconnected metalwork, thus amplifying audible transformer hum.
When windings surround the core, the transformer is core form; when windings are surrounded by the core, the transformer is shell form.
Understanding Vector Group of Transformer (part 1)
At higher voltage and power ratings, shell form transformers tend to be more prevalent. Each lamination is insulated from its neighbors by a thin non-conducting layer of insulation. Thinner laminations reduce losses,  but are more laborious and expensive to construct.
- Step-Up Vs. Step-Down Three-Phase Transformers
Laminating the core greatly reduces eddy-current losses One common design of laminated core is made from interleaved stacks of E-shaped steel sheets capped with I-shaped pieces, leading to its name of 'E-I transformer'.
The cut-core or C-core type is made by winding a steel strip around a rectangular form and then bonding the layers together. It is then cut in two, forming two C shapes, and the core assembled by binding the two C halves together with a steel strap.
A steel core's remanence means that it retains a static magnetic field when power is removed. When power is then reapplied, the residual field will cause a high inrush current until the effect of the remaining magnetism is reduced, usually after a few cycles of the applied AC waveform.Transformers Physics Problems - Voltage, Current & Power Calculations - Electromagnetic Induction
On transformers connected to long, overhead power transmission lines, induced currents due to geomagnetic disturbances during solar storms can cause saturation of the core and operation of transformer protection devices. The higher initial cost of the core material is offset over the life of the transformer by its lower losses at light load.
RELATIONSHIP BETWEEN PRIMARY AND SECONDARY WINDINGS
These materials combine high magnetic permeability with high bulk electrical resistivity. For frequencies extending beyond the VHF bandcores made from non-conductive magnetic ceramic materials called ferrites are common. Toroidal cores[ edit ] Small toroidal core transformer Toroidal transformers are built around a ring-shaped core, which, depending on operating frequency, is made from a long strip of silicon steel or permalloy wound into a coil, powdered iron, or ferrite.
The closed ring shape eliminates air gaps inherent in the construction of an E-I core. The primary and secondary coils are often wound concentrically to cover the entire surface of the core. This minimizes the length of wire needed and provides screening to minimize the core's magnetic field from generating electromagnetic interference. Toroidal transformers are more efficient than the cheaper laminated E-I types for a similar power level.
Other advantages compared to E-I types, include smaller size about halflower weight about halfless mechanical hum making them superior in audio amplifierslower exterior magnetic field about one tenthlow off-load losses making them more efficient in standby circuitssingle-bolt mounting, and greater choice of shapes. The main disadvantages are higher cost and limited power capacity see Classification parameters below.