MGVCL Exam Paper (30-07-2021 Shift 1)
A transformer designed for operation at 60 Hz supply is working at 50 Hz supply system without changing its voltage and current ratings. Compared to the full load efficiency at 60 Hz, the full load transformer efficiency at 50 Hz.

increases by 30%
increases marginally
decreases marginally
remains unaltered

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MGVCL Exam Paper (30-07-2021 Shift 1)
The expression for voltage regulation of a short transmission line for lagging power factor is given by: ___, where, 'I' is the line current, 'V_r' is the receiving end voltage, 'R' is the line resistance and 'X' is the line reactance.

(IR cosφ_r - IX sinφ_r)/V_r
(IX cosφ_r + IR sinφ_r)/V_r
(IR cosφ_r + IX sinφ_r)/V_r
(IX cosφ_r - IR sinφ_r)/V_r

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