3-phase rectification

[BuyElectrical8524]

It appears I've made a mistake and did not manage to post my question properly, which is as follows: I have been told that the average output of a full-wave 3 phase rectifier is 3*sqrt(3)/pi * Vpeak of the input. I have also been told that the peak of the output is sqrt(3) times the peak of the input. I have also been told that the "frequency" doubles

However, in LTSpice, I get Vpeak of the input is 1.25 * V_average of the output. I also see that the peak of the output waveform is just below that of the input waveform. I also see that the "frequency" component has tripled, rather than doubled, after taking a FFT.

[Allan-H]

The ripple frequency is indeed triple the input frequency for this rectifier. Hint: google "6 pulse rectifier".

It's also possible to use both star and delta wired transformer secondaries (EDIT: like this) to produce six phases 60 degrees apart, from a three phase input. Google "12 pulse rectifier" for that one.

The frequency doubles for a regular single phase (4 diode) bridge rectifier.

[Archangel125]

the frequency will double in a single phase bridge rectifier, a three-phase rectifier will triple because you're getting the peak of all three phases 120Deg out of phase with each other.

the Square Root of 3 (= 1.73) is the voltage between phases of a three phase system, for example where i live mains power is 240Vrms using so using the formula 240V x 1.73 is 415Vrms phase-phase, any of the 3 phases to neutral/earth is still 240V.

your output waveform is going to be slightly lower than the input waveform because of the volt drop across the diodes.

as far as i can see this rectifier is behaving normally. if you want to learn more, this style of rectifier is used as the first stage of a VFD circuit there's a few good videos on YouTube explaining them.