39. Fault incident on voltage Fault incident on voltage
zero point results inzero point results in
Asymmetrical current waveAsymmetrical current wave
53. In inductive circuits the current normally lags the voltage by 90, and magnetic flux isIn inductive circuits the current normally lags the voltage by 90, and magnetic flux is
normally in phase with the inductive magnetizing current that has created it.normally in phase with the inductive magnetizing current that has created it.
Therefore, at the transformer energization instant the required magnetic flux shouldTherefore, at the transformer energization instant the required magnetic flux should
be at 90, to correspond to the high-side zero-voltage point. But the transformerbe at 90, to correspond to the high-side zero-voltage point. But the transformer
magnetic circuit has no flux, and as a result the flux must start at the zero point andmagnetic circuit has no flux, and as a result the flux must start at the zero point andmagnetic circuit has no flux, and as a result the flux must start at the zero point and
overshoot to twice the maximum value during the first voltage cycle. This will causeovershoot to twice the maximum value during the first voltage cycle. This will cause
core saturation, forcing the generation of a sharp unidirectional peakingcore saturation, forcing the generation of a sharp unidirectional peaking
nonsinusoidal magnetizing current waveform that may persist for several seconds.nonsinusoidal magnetizing current waveform that may persist for several seconds.