Category: SINGLE-PHASE TRANSFORMERS

The transformers are often classified according to their applications. Following are the important types of transformers: 10.31  POWER TRANSFORMER AND ITS AUXILIARIES The transformers used in the power system for transfer of electric power or energy from one circuit to the other are called power transformers. The rating of a transformer includes voltage, frequency, and kVA.…

Fig. 10.39  Auto-transformer as a variac Example 10.40 Determine the core area, the number of turn, and the position of the tapping point for a 500 kVA, 50 Hz single phase, 6600/5000 V autotransformer, assuming the following approximate values: emf per turn 8 V, maximum flux density 1.3 tesla. Solution: We know,   E = 4.44 f BmAiN or…

Although autotransformers have less cost, better regulation and low losses as compared ordinary two-winding transformer of same rating. But still they are not widely used due to one major disadvantage that the secondary winding is not insulated from the primary. If an autotransformer is used to supply low voltage from a high voltage and there…

Volume, and hence weight of copper (or aluminium), is proportional to the length and area of X-section of the conductor. The length of conductor is proportional to number of turns, whereas area of X-section is proportional to the current flowing through it. Hence, the weight of copper is proportional to the product of current and number of…

At first sight, an autotransformer appears to be similar to a resistance potential divider. But this is not so, as described below.

A transformer, in which a part of the winding is common to both primary and secondary circuits, is called an autotransformer. In a two-winding transformers, primary and secondary windings are electrically isolated, but in an autotransformer, the two windings are not electrically isolated rather a section of the same winding acts as secondary or primary…

All the transformers are tested before placing them in the field. By performing these tests, we can determine the parameters of a transformer to compute its performance characteristics (like voltage regulation and efficiency.). To furnish the required information, open circuit and short circuit tests are conducted conveniently without actually loading the transformer. 10.23.1  Open-circuit or No-load…

The efficiency discussed so far is the ordinary or commercial efficiency which is given by the ratio of output power to input power, that is, Commercial efficiency, The load on certain transformers fluctuate throughout the day. The distribution transformers are energized for 24 h, but they deliver very light loads for major portion of the…

The efficiency of a transformer is defined as the ratio of output to the input power, the two being measured in same units (either in watts or in kW). Transformer efficiency,  or Where V2 = Secondary terminal voltage I2 = Full-load secondary current cos ɸ2 = p.f. of the load Pi = lron losses = Hysteresis losses + eddy current losses        (constant…