# misunderstanding of Voltage output of a 3-phase rectifier

I simulated a 3 phase rectifier :

I obtained V1 and V2 as plotted below :

I dont understand that waveform as i'm supposed to obtain a DC voltage. Can someone explain me how it comes that i got this waveform ?

• Are your three phases 120 degrees out of phase with each other? Commented Feb 13, 2020 at 16:14
• the resolution is horrible... why do we see 20 cycles of the same waveform but I can't even read the magnitude of the voltages? I am pretty sure that your waveform are in opposing sign meaning if you would do the voltage measurement between you would obtain an DC. Commented Feb 13, 2020 at 16:27
• The circuit should be grounded at only one point.
– user80875
Commented Feb 13, 2020 at 16:32
• Make your plot bigger so we can read the y-axis. I think that's just ripple and you haven't noticed it doesn't drop all the way down to zero. The extra ground on the left is mucking a bit with things though but shouldn't destroy it. You get better results without it. Commented Feb 13, 2020 at 16:50
• What happens if you remove the ground from the AC sources? Commented Feb 13, 2020 at 17:40

Your V2 polarity is backwards. You want the minus side on ground.

Your circuit is probably working. As it is, both of your outputs are plotting positive, and all you see is ripple. We need to see your plot axis labels to know for sure.

It works in CircuitLab (guessing at what you think that it should do)

simulate this circuit – Schematic created using CircuitLab

Edit: Plot with left ground removed. DKNguyen is correct, it works much better without the ground on the left. Only a few tenths of a volt of ripple.

• Thank you @Mattman944 The fact is that this schematic is a transcription of a real test bench, the 3ph sinusoidal power supply is the output of a Δ-Y transformer, the Y winding has a neutral point that we connect to the ground. Should i disconnect the right ground ? Commented Feb 14, 2020 at 13:25
• @TESLA - I don't know for sure. Others are saying that the left ground should be disconnected, this makes sense to me, but I am not an expert on this. You may need to ask another question. If you do, realize that many people only remain interested in a question for a few hours. If you don't respond to comments quickly people will lose interest. Also, link to this question. Commented Feb 14, 2020 at 13:33
• you are right. Thank you for your answers. Commented Feb 14, 2020 at 15:22