Core type and Shell type Transformer Depending upon the type of construction used, the transformers are classified mainly into two categories i.e Core type and shell type Core Type In core type construction ,the coils are wound around the two limbs of a rectangular magnetic core. Each limbs carries one half of the primary winding … Read more
Polarity Test On the primary side of a two winding transformer, one terminal is positive with respect to other one. At the same time ,one terminal of the secondary winding is positive with respect to other one. Polarity test is performed to determine the terminals having the same instantaneous polarity. The relative polarities of the … Read more
Grounding Transformer The neutral or star point is usually available at every voltage level form generator or transformer neutral .However if no such point is available due to delta connections or if neutral point is desired on bus-bars,a Zig-Zag transformer is most commonly used .Zig-Zag transformer has no secondary .Zig-Zag transformer is core type transformer … Read more
Choice of Transformer connections 1.Star-star(Yy0 or Yy6) connections:This type of Transformer is most economical for small current and high voltage transformers. Advantages: The number of turns per phase and the amount of insulation is minimum because phase voltage =1/√3 of line voltage. There is no phase displacement between the primary and secondary voltages. It is possible … Read more
Open-circuit Test(or No -Load Test) Open-circuit test is used to determine the : core(or iron excitation) loss,Pi No-load current ,Io shunt branch parameters Ro and Xo of equivalent circuit. Open circuit Test on transformer In open circuit test usually high-voltage winding is kept open circuited and the rated voltage at rated frequency is applied to … Read more
Transformer Efficiency Definition: The efficiency of Transformer(η) is defined as the ratio of useful power output to the input power,the two being measured in same units(either in watts or kilowatts). i.e Transformer efficiency, Now power output=V2I2cosΦ where, V2=secondary terminal voltage on load I2=secondary current at load and cosΦ=power factor of the load. Iron loss,Pi=Hysteresis loss+eddy … Read more
Voltage regulation Definition: Voltage regulation of a Transformer is defined as the change in magnitude of terminal voltage or secondary voltage,when full load(rated load) of specified power factor supplied at rated voltage is thrown off(reduced to no load) with primary voltage and frequency held constant,as percentage of the rated terminal voltage. Explanation of voltage regulation … Read more
Transformer on No load The transformer is said to be at no load when the primary of a transformer is connected to the source of ac supply and the secondary is open. We consider an ideal transformer whose secondary side is open and the primary winding is connected to a sinusoidal alternating voltage V1. Due … Read more
Ideal Transformer Definition:Certain idealizing assumptions are made for better understanding and for a very easier explanation of a practical transformer.A Transformer having these ideal properties is hypothetical and refereed to ideal transformer.Ideal transformer posses certain features of a real transformer and some of idealizing assumptions are made which will be described below: No winding resistance:The … Read more
Emf equation When an alternating(sinusoidal) voltage is applied to the primary winding of a Transformer an alternating(sinusoidal) flux is produced in the iron core which links both the windings i.e primary as well as secondary.The derivation of Emf equation of transformer is shown below: Method 1 Let Φmax=maximum value of flux in webers f=supply frequency in … Read more