Category Archive for: «Transformers»

How To Reduce Transformer Losses At Design Stage

Design changes to reduce transformer losses Design changes to reduce transformer losses, just as in a motor, always involve trade offs. For example, consider varying the cross-sectional area of the transformer core. An increase tends to lower no-load loss while raising the winding loss. An increase in volts per turn reduces winding loss while increasing […]

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Better understanding of transformer failures and maintenance necessity

Transformer failures Generally speaking, the transformer requires less care compared to other electrical equipment. But, as I already stated in some of the earlier technical articles, transformer failures can cause a huge problem in power system, since it’s one of the most critical link and it can take a while to replace if it fails. Let’s […]

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10 Factors To Consider When Specifying Transformers

Guidelines to specifying transformers The following ten factors MUST be considered when specifying transformers // Kilovoltampere (kVA) Rating Voltage Ratings, Ratio, and Method of Connection (Delta or Wye) Voltage Taps Typical Impedance Values for Power Transformers Insulation Temperature Ratings Insulation Classes Sound Levels Effects of Transformer Failures Harmonic Content of Load Paralleling transformers 1. Kilovoltampere (kVA) […]

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3 Main causes of false differential current in transformer

Differential current // Certain phenomena can cause a substantial differential current to flow, when there is no fault, and these differential currents are generally sufficient to cause a percentage differential relay to trip. However, in these situations, the differential protection should not disconnect the system because it is not a transformer internal fault. Such phenomena can be […]

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Matching transformers for parallel operation

3 rules for parallel transformers // The following rules must be obeyed in order to successfully connect two or more transformers in parallel with each other: The turns ratios of all of the transformers must be nearly equal. The phase angle displacements of all of the transformers must be identical. The series impedances of all […]

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Do dry type transformers really cost less?

Comparison to dry type transformers To many industrial and commercial organisations dry type transformers are seen to be advantageous compared with oil filled units. They avoid the perceived fire risk of oil filled transformers and can thus be accommodated inside a building or even on the roof of an office block. Savings can be made […]

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Practical Considerations of LV/MV Private Substations

Private substations Private substations can often be considered as terminal type substations, i.e. substations where the MV line ends at the point of installation of the substation itself. They belong to the user and can supply both civil users (schools, hospitals, etc.) with power and industrial users with supply from the public MV grid. These […]

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Practical Considerations Of Transformer Inrush Current

Inrush current phenomenon When a transformer is initially connected to a source of AC voltage, there may be a substantial surge of current through the primary winding called inrush current. This is analogous to the inrush current exhibited by an electric motor that is started up by sudden connection to a power source, although transformer inrush […]

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Guidelines For Installing Power Transformers

Operation of power transformers // When your transformer arrives on site, various procedures should be carried out to assure successful operation (installation, testing and various checkings). The successful operation of a transformer is dependent on proper installation as well as on good design and manufacture. The instructions mentioned in the manufacturer manual or in Standards […]

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5 conditions for perfect parallel operation of single phase transformers

Parallel operation of transformers // In perfect parallel operation of two or more transformers, current in each transformer would be directly proportional to the transformer capacity, and the arithmetic sum would equal one-half the total current. However, there are 5 conditions for operating transformers in parallel and they are: Any combination of positive and negative […]

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