Yes with Vienna rectifier you can reach unity power factor but
you need the neutral wire. If you have only the 3phases without
neutral this is the only way to go.
Vienna brigde is related to very high power systems, at those power level is not justified to to its complexity.
Altough the current is not sinusoidal the power factor is around 0.95, compared to the typical 0.55 of a bridge+capacitor you can quite divide by two the RMS current in the phases for a given power.
you need the neutral wire. If you have only the 3phases without
neutral this is the only way to go.
Vienna brigde is related to very high power systems, at those power level is not justified to to its complexity.
Altough the current is not sinusoidal the power factor is around 0.95, compared to the typical 0.55 of a bridge+capacitor you can quite divide by two the RMS current in the phases for a given power.
It doesn't need the neutral, but on the other hand it needs three inductors.
http://en.wikipedia.org/wiki/File:Vienna_rectifier_schematic.jpg
Another alternative is using three controllable half-bridges like in a motor inverter, but doing that needs three inductors and six IGBTs with diodes. Cheating is probably OK though, PF is very high if constant current is pulled out of the rectifier bridge although the current drawn won't be sinusoidal.
http://en.wikipedia.org/wiki/File:Vienna_rectifier_schematic.jpg
Another alternative is using three controllable half-bridges like in a motor inverter, but doing that needs three inductors and six IGBTs with diodes. Cheating is probably OK though, PF is very high if constant current is pulled out of the rectifier bridge although the current drawn won't be sinusoidal.
rcavictim said:
I appreciate your sense of humour
These modern solid state things are actually lovely when you use them properly. They allow to do very powerful things in little space and producing little heat. In the old days you couldn't do amplifiers (or power supplies) capable of 3, 4 or 5KW in half the size of a shoe box and efficient enough to do full music output without even a fan. Now I have one of these on top of my bench, 15W idle consumption, 10KW peak output
and no fireworks. It makes lights dim with bass transients, the 230V mains supply now looks like the 12V electrical system of a car Some of the parts that I use weren't even available before 2006.Orcino is having trouble because he is inexperienced and he just ignores the parts of our advice that he doesn't like or doesn't understand
But his circuit would work with some (drastical) changes (not involving migration to tubes ).
That circuit is surprisingly similar to the one in the Prius inverter. The motor/generator windings act as the inductors. The voltage from the motor/generator is normally too low for regenerative braking at low speed, so the low side IGBTs are PWMed and the high speed rectifiers in parallel with the high side IGBTs rectify the pulses. Essentially a 3 phase boost PFC rectifier that can return to inverter operation under logic control.megajocke said:
http://techno-fandom.org/~hobbit/cars/boost-hack/
To really appreciate what modern power electronics can do, first look under the hood of a hybrid car and note how small the inverter is. Then get in the car, drive to a race track, and accelerate hard. Afterwards, look at the inverter again and think of how much power it just handled.Eva said:
I appreciate your sense of humour
These modern solid state things are actually lovely when you use them properly. They allow to do very powerful things in little space and producing little heat. In the old days you couldn't do amplifiers (or power supplies) capable of 3, 4 or 5KW in half the size of a shoe box and efficient enough to do full music output without even a fan. Now I have one of these on top of my bench, 15W idle consumption, 10KW peak output
Orcino is having trouble because he is inexperienced and he just ignores the parts of our advice that he doesn't like or doesn't understand
Or better yet, do that with a hybrid racing bicycle. Be amazed as that little inverter hurls your bike to speeds even Lance Armstrong cannot match. It might even be more fun than racing a car.
Actually, the so-called active-front-end PFC consists of 3 half-bridges (as megajocke mentioned) and works exactly the same way and uses exactly the same topology as motor inverter at regenerative braking mode.
Needless to say, it can also reverse the power flow and source the power back to the mains, something Viennna bridge cannot do.
Needless to say, it can also reverse the power flow and source the power back to the mains, something Viennna bridge cannot do.
How is the waveform for gate IGBTs for this type of switching ? ( full-bridge no ZVS ). Thnks again.
star882 said:
I know that very special way of feeling (many would not understand) but I experience it mostly with audio amplifiers and high efficiency speakers, particularly when you get a lot of clean sound outdoors, for many people to feel enjoy, using very little power.
On the other hand, the inverter on the prius is supposed to do 30kw peak per motor, isn't it? The layout does not suggest a particularly good handling of parasitics and the related voltage overshoot, I bet it could be improved to, at least, do the same job producing less heat. On my current project I'm switching up to 40A 180V per TO-220 device, and they don't fail, the limiting factor is dissipation on such a small package.
To Orcino:
IGBT gate waveforms look much like MOSFET ones, but with a higher plateau voltage, you should have never started this project without having seen any
I will try to make some MOSFET captures for you since I don't have anything with IGBT handy.What you have to ensure is that the IGBT are not turning on when they shouldn't, for example due to erratic signal coming from microcontroller or wiring/PCB parasitics, or due to transients coupled by collector-gate capacitance. You have also to ensure that the voltage on IR2113 outputs never goes more than 0.2V-0.3V below the corresponding ground pin, since this results in latch-up and bang!
Also, how do you expect flux balancing in the transformers to happen? There is no series DC blocking capacitor and no peak current control. In fact, the expected natural behaviour of the circuit that you posted is to self destruct
If it's able to produce some output power before that happents, it's purely incidental.Same applies for the PFC input rectifier. The concept is wrong.
btw: The switching nodes of the half bridge don't rest exactly in the middle of the supply voltage during dead time, giving that asymmetrically stepped waveform, because it's almost impossible to get exactly equal switching times on both half briges. That's why DC blocking or peak current control is required.
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