transformer utilization factor

[p11]

for half wave rectifier for 1 half of the input cycle the transformer secondary is unused .but for centre tap full wave rectifier for both halves 1 half of the 2ndary is used. for the bridge rectifier however the entire 2ndary is used for both the halves . so T.U.F of half wave < full wave < bridge rectifier . am i correct ? but i think TUF of primary winding in all the 3 cases should be same .is it ?

 

[D.A.(Tony)Stewart]

Although slightly more current, for same temp rise ,, more ripple, but less power . so less efficient for your example.

Better half wave uses full winding and negative clamp.

 

[BradtheRad]

Tiny current flows in the primary when no current flows in the secondary.

An efficient design characteristic of power transformers is that they should draw minimal power.

 

[FvM]

but i think TUF of primary winding in all the 3 cases should be same .is it ?

You should sketch the primary waveform of the half-wave rectifier and estimate it's RMS current to answer the question. No, it's not the same utilization factor.

An additional important reason why a half wave rectifier can't work with good efficiency is the core DC magnetization.

 

[Easy peasy]

Utilisation factor highest for single winding o/p with 4 diodes doing the rectifying, for a CT rectifier (2 diodes) the current in each winding is 0.707 of that in the single winding (and there are two f them) - so there is a penalty for CT o/p's...

Single winding o/p can also have voltage doubler with 2 diodes and two caps...
and current doubler with 2 diodes, 2 inductors...

All other config's are lower utilisation than CT o/p...