We can observed from the circuit diagram that when the diode is
reversed biased then full transformer secondary voltage gets impressed
across it. The drop across conducting diode is assumed zero. Thus the
peak value of the inverse voltage to which diode gets subjected is
voltage across both the parts of the transformer secondary. This is
shown in the Fig. 1.

Fig. 1 |

When D

where E_{2}is reverse biased, point A is at - E_{sm }with respect to ground while point B is at + E_{sm }with respect to ground, neglecting diode drop. Thus total peak voltage across D_{2}is E_{sm}._{sm }= Maximum value of a.c. voltage across half the secondary of transformer.

If the diode drop is considered to be 0.7 V then the PIV of reverse biased diode is,

This is because only one diode conducts at a time.

__1.12 Transformer Utilization Factor (T.U.F.)__

In full wave rectifier, the secondary current flows through each half
separately in every half cycle. While the primary of transformer carries
current continuously. Hence T.U.F. is calculated for primary and
secondary windings separately and then the average T.U.F. is determined.

_{f }of diode, E

_{sm }≈ I

_{m }R

_{L}.

The primary of the transformer is feeding two half-wave rectifiers
separately. These two half-wave rectifiers work independently of each
other but feed a common load. We have already derived the T.U.F. for
half wave circuit to be equal to 0.287. Hence

T.U.F. for primary winding = 2 x T.U.F. of half wave circuit = 2 x 0.287 = 0.574.The average T.U.F. for fullwave circuit will be

Average T.U.F. for full wave rectifier circuit = (T.U.F. of primary + T.U.F. of secondary)/2

= (0.574 + 0.812)/2 = 0.693

**.**Average T.U.F. for full-wave rectifier = 0.693

^{.}.**Note**: Thus in full-wave circuit, transformer gets utilized more than the half wave rectifier circuit.

__1.13 Voltage Regulation__

The regulation can be expressed as,

and I

_{DC }= 2I

_{m}/π

Neglecting winding resistance, the regulation can be expressed as,

where R

_{f }= Forward resistance of the diode.

The regulation characteristics is drooping, as we see earlier in case
of half wave rectifier as output voltage decreases as load increases
from no load to full load.

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