Material commonly used in making transformer core is

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high silicom steel Explanation: High silicon steel is the standard material used for transformer cores because it possesses high magnetic permeability and high electrical resistivity. The addition of silicon (typically 3-5%) reduces hysteresis loss and eddy current loss, significantly improving the transformer's efficiency. Working Principle: The core acts as a low-reluctance path for magnetic flux, which is generated by the primary winding. Silicon steel is used because its grain-oriented properties minimize energy dissipation during the rapid magnetic polarity reversals (hysteresis) and reduce circulating currents within the core (eddy currents). By increasing resistivity, the silicon content limits the magnitude of eddy currents, following the relation $P_e \propto \frac{1}{\rho}$, where $\rho$ is the resistivity of the core material. Key Formulas: $P_h = K_h f B_{max}^{1.6}$ — Steinmetz hysteresis loss formula; $P_e = K_e f^2 B_{max}^2 t^2$ — Eddy current loss formula Key Points: Silicon steel minimizes hysteresis loss by lowering the area of the B-H loop.; Lamination of the core reduces the effective path for eddy currents, further decreasing losses.; Grain-oriented silicon steel (CRGO) is preferred for high-efficiency transformers.; High resistivity of silicon steel reduces circulating current heating. Advantages: Lower power loss (high efficiency); High magnetic permeability; Improved thermal stability Disadvantages: Increased material brittleness; Higher initial cost compared to mild steel Applications: Power transformers; Distribution transformers; Electrical inductors Additional Info: Cast iron has very high hysteresis loss and is unsuitable for transformer cores.. Mild steel has higher eddy current losses due to lower resistivity.. Silicon content is usually kept under 5% to prevent the material from becoming too brittle for manufacturing processes. Answer: C is correct — High silicon steel is the standard material used for transformer cores to minimize energy losses due to its high magnetic permeability and resistivity. Exam Tip: Always remember that in electrical machines, 'efficiency' is the primary driver for material selection; hence, minimize both Hysteresis (area of loop) and Eddy (resistivity) losses.

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