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| 3-phase "equalisation" transformer? |
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| Circlotron:
Is there some kind of three phase transformer that could perform the function of making the voltage of all three phases equal? Assuming the supply has a certain impedance and so is able to be pushed about a bit, e.g an alternator of say 5kVA, could a transformer of sorts take action if the sum of the instantaneous voltage of all three phases at any given moment was not zero, and either inject or draw current from the offending phase? I'm not talking about autotransformer action or a tap switcher, just something that would try and correct voltage imbalance by a corresponding and opposite current imbalance. As mentioned, the source would have to have some sort of impedance for this to work. Definitely not for connection to AC mains! |
| NiHaoMike:
https://en.wikipedia.org/wiki/Zigzag_transformer |
| soldar:
I do not think the zig-zag transformer does what the OP is asking but I would need more information on what exactly he is trying to do. If the voltage of one phase, in a three phase system, sags it means it is loaded more than the other phases. The only way I can think you could maintain voltage is by using (auto)transformer or re-arranging the loads of the other phases. |
| Circlotron:
--- Quote from: soldar on July 31, 2019, 10:19:18 pm ---I do not think the zig-zag transformer does what the OP is asking but I would need more information on what exactly he is trying to do. --- End quote --- I'm just messing around on the bench doing experiments, nothing practical. I have a 50 watt 2-channel audio power amplifier driven by two sine waves 60 deg apart. (yes, 60 deg, not 120 deg) The outputs of the amplifiers drive the primaries of three 28V-240V transformers, the primaries connected in delta with the third connection grounded. The secondaries are also delta connected and driving a ~1/4hp 6 pole induction motor. Rated motor speed is 1000rpm @ 50Hz. I can get it to run to almost 6000 rpm but the voltage is only 150VRMS, not nearly high enough, so raising the frequency further causes the motor to slow down. The phase voltages are almost perfectly balanced and it is not a problem as such, but what I was looking for is something that would lock the phase voltages together by brute force somehow. If one phase voltage was a little low or high it would pull current from, or send current to the other phases somehow. Electrical engineering is one of those disciplines that appears simple until you start digging into it! |
| Circlotron:
Is it possible to make a zig zag transformer using 3 single phase transformers? If so, what would the turns ratio be? 1:1? |
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