A transformer is mainly a passive electrical device that transfers or helps in transferring the powerful electrical energy from one electrical circuit to another one, it can also work with multiple circuits.
Transformers are mainly used for increasing the AC voltages which are low at high current (a step-up transformer) or reducing the amount of the high AC voltages at low current (a step-down transformer) in electric power applications. Transformers can also be used for isolation, in many cases.
Transformers also act in the process of raising the voltage from electric generators so that the electric power can be transmitted over long distances.
Transformers change voltage through the process of electromagnetic induction, i.e., as the magnetic lines of force (flux lines) build-up with the changes in the passing of the current through the coil, current is being induced in the other coil, named as the secondary one.
Air-core transformers are developed and used to transfer radio-frequency currents—which is, the currents being used for the radio transmission; they have two or more than two coils wound around a solid insulating substance or on an insulating coil form. There are many good transformer manufacturers to help you in selecting the best transformer for you.
There are various types of transformers to help you:
Among an array of different types of transformers, some of them are, step up and step down transformers, distribution transformer, power transformer, instrument transformer, single phase and three phase transformer, auto transformer and instrument transformers.
Depending on the types of construction, transformers are divided into two categories, the Core type and the Shell type. These two types are different from each other by the way in which the primary and secondary coiled are located around the steel core.
There are several factors which can have a big influence on the function of a transformer. Here is a precise discussion on the tips to help you before you buy a transformer:
1. Voltage Ratio, Ratings and Process of Connection
All the good and most wanted kVA ratings are not available as standard at all voltage ratings and ratios. In most cases, the smaller sizes apply to lower voltages and the larger ones apply to higher voltages.
Voltage ratings and ratios should be identified in following the available standard equipment that is indicated in the catalogues of a good manufacturer of transformers. This is recommended, and if possible, both from the aspects of cost and time for initial requirement and for ready replacement, if necessary.
Generally, a three-phase transformer for the use of secondary voltage should be selected at 480Y/277 V. This is the actual standard and has good compatibility with three-phase motors, which are rated 460 V standards now days.
2. Voltage Taps
Taps are used to change or alter the ratio between the high- and low-voltage scales. Manual de-energized tap changing in many cases is used to compensate for the differences or fluctuations between the transformer ratio and the system voltage, which is nominal. The tap selected in the transformer should have to be on the basis of the maximum no-load voltage conditions.
Taps can be altered when the transformer is loaded and is charged with energy. These taps are used to compensate for excessive fluctuations or differences in the supply of the required voltage. They are also in some cases associated with commercial building.
Taps can be changed also at the time only when the transformer is de-energized.
Manually adjustable taps are good for correcting the conditions of the long-term voltages. But those are not good for correcting short-term voltage variations.
3. Typical Impedance Values for Power Transformers
Non-standard impedances can be mentioned at a higher cost: Higher impedances to reduce the already present fault currents or lower impedances to reduce the drop of voltage under the heavy-current, or the conditions of low-power factor surge. When specifying the good transformers, best would be to consult the bulletin of top transformer manufacturing companies for impedances of small transformers because they can fluctuate at any time considerably.
4. Insulation Temperature Ratings
Transformers are created and developed with various insulation material systems.
The transformers with lower conductor losses and the rises in the corresponding lower temperature are available, when longer life expectations and reduced operating costs are preferred.
5. Sound Levels
Good sound level of a transformer can be a problem in commercial building interiors, especially in those areas where relative quiet is mainly preferred, such as in conference rooms and certain areas of an office or company.
6. Effects of Transformer Failures
Transformer failures are actually some rare incidents. However, in high-rise buildings and in many other types of buildings where the conditions of immediate evacuation is very limited, the results of the failure of a larger transformer can be a cause of big concern. Air from transformer vaults always should be exhausted directly to the outside areas. Dry type transformer manufacturers and exporters produce the ones which are safer as they are less-flammable. These ones are suitable at places where the fire and smoke can turn into critical factors.
7. Harmonic Content of Loads
Very recent developments have showed the failures of some particular types of transformers due to loads which are not linear, which is the main cause of the flow of third and higher harmonics through the windings.
When these harmonics are available, due to loads like computers, variable speed drives, electronic ballasts, rapid mode switching devices, HID lightings, and similar electrical loads, preference should be given to a special transformer which is designed to face these harmonic currents and also the fluxes which are being produced in the cores.
8. Paralleling transformers:
When a transformer is being paralleled with another one is called as the process of paralleling transformers.
9. KVA rating:
An important factor is considering the KVA rating. This is calculated from the primary and secondary voltage information. You can easily select a good transformer on that basis.
Physical size is a very important aspect while choosing a transformer. Many transformers have different sizes to fit within your preferred spaces.