Winding Resistance Test DefinitionThe winding resistance test of a transformer checks the health of transformer windings and connections by measuring resistance.Procedure of Transformer Winding Resistance MeasurementFor star connected winding, the resistance shall be measured between the line and neutral terminal.For star connected autotransformers the resistance of the HV side is measured between HV terminal and IV terminal, then between IV terminal and the neutral.For delta connected windings,

Temperature Rise Test DefinitionA temperature rise test of a transformer checks if the temperature increase of its winding and oil meets specified limits.Temperature Rise Test for Top Oil of Transformer First, the LV winding of the transformer is short-circuited. Then one thermometer is placed in a pocket in the transformer top cover. Other two thermometers are placed at the inlet and outlet of the cooler bank respectively. The voltage of such value is applied to the HV winding that power input

Dielectric Test DefinitionThe dielectric test of a transformer checks the insulation’s ability to handle voltage without breaking down.Separate Source Voltage Withstand Test of TransformerThis dielectric test checks the main insulation’s ability to withstand voltage between the winding and the earth.Procedure All three line terminals of the winding to be tested are connected together. Other winding terminals not under test and the transformer tank should be connected to the earth. Then a single-

Vector Group Test DefinitionThe vector group test of a transformer checks the phase sequence and angular difference to ensure transformers can operate in parallel.Vector Group Test of TransformerThe vector group of a transformer is essential for successful parallel operation of transformers. Every electrical power transformer must undergo a vector group test at the factory to ensure it matches the customer’s specified vector group.The phase sequence, or the order in which phases reach their peak

Transformer DefinitionA transformer is defined as an electrical device that transfers electrical energy between two or more circuits through electromagnetic induction.Theory of Transformer on No-LoadHaving No Winding Resistance and No Leakage ReactanceConsider a transformer with only core losses, meaning it has no copper loss or leakage reactance of transformer. When an alternating current source is applied to the primary, it supplies current to magnetize the core of transformer.But this current

Losses in TransformerAs 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 c

Leakage Reactance DefinitionIn a transformer, not all the flux links both the primary and secondary windings. Some flux links with only one winding, called leakage flux. This leakage flux causes self-reactance in the affected winding.This self-reactance is also known as leakage reactance. When combined with the transformer’s resistance, it forms impedance. This impedance causes voltage drops in both the primary and secondary windings.Resistance of TransformerThe primary and secondary windings of

Eddy Current DefinitionAccording to Lenz’s law, when a conducting loop is exposed to a changing magnetic field, it generates an emf that induces a current opposing the change. Similarly, when a magnetic field changes through a conducting body, like a filament or a slab, it causes currents to flow through the material’s cross-sections.These currents are given the name eddy currents after the water eddies that are small swirling whirlpools observed in lakes and oceans. These eddy current loops can

Transformer Cooling System

Transformer Banking