Can a 50 Hz transformer be used as 25 Hz, if the input voltage is maintained constant at the rated corresponding to 50 Hz?
1. Yes, since the voltage is constant, current levels will not change
2. No, flux will be doubled which will drive the core to excessive saturation
3. No, owing to decreased reactance of transformer, input current will be doubled at load
4. Yes, at constant voltage, insulation will not be overstressed