While finding various factors of single-phase diode rectifiers, the transformer utilization factor of a half-wave rectifier is  

TUF: The transformer utilization factor (TUF) is the measure of merit of a rectifier circuit.

It is defined as the ratio of dc power output to the transformer Volt-Ampere (VA) rating required by the secondary winding.

TUF = (DC power output) / (Effective VA rating of transformer)

\(TUF = K = \;\frac{{{P_{dc}}}}{{{V_s}{I_s}}}\)

It is a quantitative indication of the utilization of VA Rating of Transformer. The more the value of TUF, the more will be the utilization. In other words, the VA rating of the required transformer will be less if TUF is more and vice versa.

NOTE: 1/TUF for full-wave bridge rectifier signifies that the transformer must be 1.23 times higher than that when it is used to deliver power from a pure ac voltage source.

Points to Remember:

• TUF for Half-Wave rectifier is 28.6%
• TUF for Full-Wave center tapped rectifier is 57.2%
• TUF for Full-Wave bridge rectifier is 81%