# How is this being done..?

#### thedoc8

Joined Nov 28, 2012
147
I came across this on a tesla coil forum and I don't understand how this circuit works. 3 separet step up transformers fed from single phase and some how getting 3 phase out 120/120/120 apart. I can only see 180 degrees apart. One transformer at 0 degrees relitive to the other 2 transformer that would be 180.

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#### LesJones

Joined Jan 8, 2017
2,605
It is not fed from a single phase. Each transformer primary is connected between neutral and one of the three phases. (One transformer per phase.)

Les.

#### bertus

Joined Apr 5, 2008
20,460
Hello,

It is stated in the picture that the three phases are 120 degrees apart.
A bit down on this page of the wiki there is a picture of a three phase rectifier:
https://en.wikipedia.org/wiki/Rectifier

Bertus

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,010
I've worked on systems that were supplied with 208 3 phase 60 A and 90 A to a single transformer with three primaries. The former developed 15 kV at 1.5 A regulated.

#### thedoc8

Joined Nov 28, 2012
147
Omg, I swear I though I read the 3 transformers were being fed single phase, just read again and it aint there. I thought someone come up with some vodo magic. Thanks for the replys.

#### Tonyr1084

Joined Sep 24, 2015
4,381
One thing confusing me - - - "Tesla Coil Forum". I'm seeing the output voltage (the AC rectified component) being an RMS value. The addition of the capacitor brings the voltage up to the full rectified voltage, meaning 1.414 times the RMS value. ( 1.414 = √2 ) Assuming this is a 1:1 transformer powered at 120 VAC then the rectified and charged (through the cap) voltage would be 120 x 1.414 = 169.68 volts DC. I don't see this being much of a high voltage in reference to the ultra high voltages I've seen Tesla (I'll call it) Lightning Machine(s).

Is this supposed to be high voltage? I imagine Tesla voltages being way way up there. But then again, I don't know much about Tesla coils.

#### KeepItSimpleStupid

Joined Mar 4, 2014
4,010
I think with the three phases of input, the amount of steady DC current goes up and the size of the filter capacitors should go down.

#### Wolframore

Joined Jan 21, 2019
1,743
the output of ratio or voltage of the transformer is not specified but it states that it is a step up transformer... I believe everything else was explained otherwise. The example shows 3 phase Y input and output.

#### Tonyr1084

Joined Sep 24, 2015
4,381
Assuming this is a 1:1 transformer
As I said originally; "Assuming this is a 1:1 transformer". The reason for making such an assumption is because there was no output stated. Establishing an assumed position allowed for the explanation of the square root of 2 being the factor to multiply the output to ascertain its peak voltage when applied to a filter capacitor. For all I know, it can be three MOT's (Microwave Oven Transformers). In the case of an output of 1kV, the capacitor would (assuming again, a cap of sufficient voltage capabilities) have to be able to handle 1.400 volts. With a 50% added buffer, a cap rated at 2.1KV would be ideal for the job. But the question was initially "how do you get three phases out of a single phase input?" The TS noted that he missed the point that they were three phases supplying each transformer.

My confusion in the matter has to do with the idea of a Tesla Coil producing HIGH voltage. And by "HIGH" I mean 1,000 KV or more. That's because I think of Tesla devices as those that produce spectacular lightning or hair raising static voltages of 50KV or more. Like I said before, I don't know much about Tesla coils and Vandergraph generators and such. That vinyl wheel with the metalized plates and wire brushes that also generate ultra high voltages and create spectacular sparks.

BUT HEY! I DON'T WANT TO HIJACK THIS THREAD. For all intents and purposes, I don't really need an answer. Sometimes I just throw things out there to spark further conversation on a given topic.