After a quarter resonance period, the capacitor voltage begins
to reverse polarity which causes the protective diode (Fig. 2)
to conduct, effectively removing the capacitor from the circuit.
Without the capacitor, the magnetizing current decays at a rate
defined by the time constant of the circuit’s resistance and inductance.
Once the current flowceases, the transformer core flux
is fixed and the prefluxing process is complete. Fig. 6 shows the
curve during prefluxing.
The shaded region of the voltage waveform in Fig. 4 and the
transformer emf waveform of Fig. 5 are very similar. Therefore,
the volt-seconds imparted on the transformer by the prefluxing
device are solved in the same manner as was done for the rated
transformer operation and are given in