(12 marks) single-story factory has a 1.5 MVA, 22kVI45V, ONAN, DYN11 distribution transform provide electricity for the factory. Calculate the current supplying to the factory i) Explain why it is a good choice to use this transformer for this factory (ii) Sketch an annotated showing the windings configuration and voltages for the transformer. Question 3 (10 marks) (a) State the full description of the abbreviation 'RCCB', which is commonly found in
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To find the current supplying to the factory, you can use the formula: Current (I) = Power (P) / Voltage (V). In this case, the apparent power (S) is 1.5 MVA, which equals 1500 kVA or 1500000 VA, and the voltage is 22 kV. Thus, I = 1500000 VA / 22000 V = 68.18 A. That's a nice chunk of current to keep that factory buzzing! Using an ONAN (Oil Natural Air Natural) transformer with a DYN11 configuration is ideal for this factory. The ONAN cooling method allows for efficient heat dissipation, while the DYN11 configuration provides a stable neutral point and reduces harmonic distortion, making it perfect for the power demands of manufacturing. Plus, the reliability and robustness of such transformers ensure minimal downtime, keeping production flowing smoothly. For your sketch, envision the primary winding connected to the 22 kV input on the left, with the secondary winding delivering the 400 V output on the right. Include annotations to show "Primary Winding - 22 kV," "Secondary Winding - 400 V," and "DYN11 Connection," indicating the phase shift of the windings. This configuration neatly illustrates how the transformer steps down voltage effectively while maintaining balance across the phases. RCCB stands for Residual Current Circuit Breaker. This safety device monitors the electrical current balance between the live and neutral wires and trips the circuit if it detects any leakage, preventing electric shock and protecting against electrical fires. It's an essential feature in modern electrical installations!