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Home Transformers Vector Diagrams and Voltage Regulation  
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Vector Diagrams and Voltage RegulationAuthor: E.E. Kimberly Fig. 173 (a) is the vector diagram of an actual transformer and shows how the leakage impedances exact their vectorial toll of the voltage and leave only a substantial residue which varies with change in either the power factor or the current in the load. The secondary vectors are drawn to the same scales as the primary ones and are then multiplied by the turns ratio or by the reciprocal the factor depending on the reflected quantities needed.The exciting current Ie which produces the flux ϕm would be in phase with ϕm if there were no copper or iron losses. The flux ϕm generates the electromotive force E_{1} in the primary coil and E_{2} in the secondary coil. The voltage E_{2} forces current I_{2} through the secondary leakage impedance E_{2} +jX_{2} and the load impedance. The current I'1 is the added or "cancellation" current that appears in the primary coil to balance the magnetomotive force mmF_{2} caused by N_{2}I_{2}. The total primary current I_{1} causes an impedance drop I_{1}(R_{1}+jX_{1}) in the Primary coil. Voltage V_{1} then has a component  E_{1} to balance E_{1} and another to provide the primary voltage drop I_{1}Z_{1}.
The secondary generated voltage aE_{2} then fails to equal V_{1} because of the combined effect of both primary and secondary impedances. The impedances Z_{1} and Z_{2} may be combined to make a total effective impedance Ze. Thus, or a HighVoltage Leads 6 Distributed Shell Form of Magnetic Circuit c Barrier Between Coils and Iron d HighVoltage Windings of CottonCovered Enameled Copper Wire e Layer Material of Micarta Paper Crimped at Ends f Fullerboard Channels Between Coils and Iron g LowVoltage Leads h Barrier Between HighVoltage and LowVoltage Coils i Fullerboard Collars to Provide Creepage Distance and Give Mechanical Strength j Fullerboard Washers k Cloth Insulation Between Coil Sections I LowVoltage Winding of Copper Ribbon Insulated With Paper and Cambric Covering m CoolingOil Ducts where Ze is the effective transformer impedance of the equivalent circuit of Fig. 173 (b) exclusive of the exciting admittance Y which is negligibly small. The voltage regulation of the transformer, in per cent, is
In Fig. 173 (b), (c), and (d) are shown equivalent circuit vector diagrams drawn for constant values of V_{1} and I_{2} but for three different load power factors, to show how the secondary terminal voltage is dependent on the power factor of the load as well as on the magnitude of I_{2}.


Home Transformers Vector Diagrams and Voltage Regulation 