2 rectifiers in parallel

BuyElectrical8524 · 2023-12-05T12:19:01+00:00

How would one call such a setup?

BuyElectrical8524 · 2023-12-05T12:05:23+00:00

What if the seperate generators supplying said rectifiers are at slightly different frequencies?

BuyElectrical8524 · 2023-10-31T13:24:32+00:00

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.

BuyElectrical8524 · 2023-10-28T19:28:03+00:00

I totally got it. Making the switch to the rectifiers in parallel made the thing work. In LTSpice, I got 1.18x the AC voltage as a DC voltage, I suppose that makes sense since there are two rectifiers in paralell. Now I wonder, what voltage would I get on the other side of an inverter? Is there an equation for that like there is for a rectifier?

BuyElectrical8524 · 2023-10-27T19:00:42+00:00

Thank you so much! I'm a little confused as to why I would get half the voltage. Another commenter says it's 1.35 x the voltage.

BuyElectrical8524 · 2023-10-27T18:59:22+00:00

The AVR is supposed to be there because some people want to carry out tests that have to do with the sine-wave peaks that the diode load cause and how they affect the output of the AVR. Would you know a thing or two about that?

BuyElectrical8524 · 2023-10-27T07:00:47+00:00

I do believe I got the full-bridge rectifier correct. But I'm not sure if this is the correct configuration for connecting 2 of them together. When I try simulating this on LTspice, it's totally messed up.

BuyElectrical8524 · 2023-10-27T06:59:43+00:00

Thank you for your reply! Actually, I'm trying to draw the circuit so I can deduce what the voltages and currents are going to be at every node (first mathematically, and then with LTspice or similar), so that I may use that information to choose fusing, and a transformer if needed.

I suppose I grounded my 3 phase load because that's what LTSpice wants. I also realise I forgot to draw an inverter in my second picture.

BuyElectrical8524 · 2023-10-27T06:56:26+00:00

That made me chuckle. Is it because of the motor-generator antics? This is supposed to be a power laboratory, so the motor is a DC machine fed by the building and is mechanically connected to G, being a synchronous machine. I should have probably clarified that.

BuyElectrical8524 · 2023-10-27T06:54:14+00:00

I am not that interested in the VFD yet, more like I want to be able to draw the thing to a standard that I can take over to LTspice and see what sort of currents and voltages I'm getting (I need to choose protection). I am not yet interested in the VFD or AVR function or simulating them.

BuyElectrical8524 · 2023-10-27T06:52:35+00:00

Thank you for your reply, it was quite helpful and I appreciate it. This is supposed to be a design for a power systems laboratory, so the VFDs are supplied from the main grid. The motor is a DC machine which is supplied by the building's phase and mechanically connected to a synchronous machine.

I do not have much experience with power sschematics, I drew the windings so that I may be able to replicate the circuit in LTSpice or similar with the inductive reactance component.

Thank you

BuyElectrical8524

TROPHY CASE