Primary winding of a transformer

Question

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Could either be a low voltage or a high voltage winding

Explanation: The terms 'primary' and 'secondary' define the electrical connection of the transformer windings, not their voltage levels. The primary winding is defined as the winding connected to the energy source, while the secondary winding is connected to the load.

Working Principle: In a step-up transformer, the primary winding has fewer turns and carries a higher current at a lower voltage. Conversely, in a step-down transformer, the primary winding has more turns and operates at a higher voltage. The transformer's classification is determined strictly by the direction of power flow.

Key Formulas: $\frac{V_p}{V_s} = \frac{N_p}{N_s} = \frac{I_s}{I_p}$ — Transformer EMF and Current Transformation Ratio

Key Points: Primary winding is defined by its connection to the source of AC power.; Secondary winding is defined by its connection to the load impedance.; A transformer can act as a step-up or step-down device depending on the configuration.; The designation 'HV' or 'LV' winding refers to the turns ratio and voltage rating, independent of which is primary or secondary.

Advantages: Versatility in power distribution systems; Allows voltage transformation for efficient transmission

Disadvantages: Potential for reversal errors if labeling is confusing; Voltage rating is specific to the design, not the primary/secondary status

Applications: Power transmission substations; Step-down distribution transformers; Isolation transformers in electronics

Additional Info: In large power transformers, windings are often classified simply as HV or LV windings regardless of their primary/secondary status.. Option A and B are incorrect because they impose a fixed voltage constraint that is not true for all transformer types.

Answer: C is correct — The primary winding is defined by the energy source connection, and it may be either a high-voltage or low-voltage winding depending on the step-up or step-down operation.

Exam Tip: When solving transformer problems, always identify the 'Source' side as Primary ($N_p, V_p$) and 'Load' side as Secondary ($N_s, V_s$) to avoid polarity or ratio errors.

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