transformer reversed connected

[Toros]

Hi
I have 3_phase loads but 1_phase servise
Can I by a 3_ phase to 1_phase xfrmer and do reverse connection????

1_phase, 240v primary to 3_phase, 208v secondary

Thank you

 

[kwired]

No, you need phase conversion equipment to derive three phase. Simple transformers will not do this.

What kind of three phase load are you supplying? That may make some difference in what is best thing to do.

 

[ggunn]

Hi
I have 3_phase loads but 1_phase servise
Can I by a 3_ phase to 1_phase xfrmer and do reverse connection????

1_phase, 240v primary to 3_phase, 208v secondary

Thank you

As kwired said, no. You can go back and forth between 240V single/split phase and 120V single phase with an autotransformer because the difference is between a single waveform and that waveform and its inverse. To get three waveforms 120 degrees apart you need to adjust the timing of (i.e., phase shift) the daughter waveforms, and there is no way to do that with transformers.

 

[GoldDigger]

As kwired said, no. You can go back and forth between 240V single/split phase and 120V single phase with an autotransformer because the difference is between a single waveform and that waveform and its inverse. To get three waveforms 120 degrees apart you need to adjust the timing of (i.e., phase shift) the daughter waveforms, and there is no way to do that with transformers.

Once you have two non-collinear phase vectors, you can use transformers alone without additional reactive elements to construct any number of evenly spaced, equal amplitude phases you want. (Scott-T to convert either way between two and three phase, in the simplest example.) So that first step between one phase and two is the qualitative one.

 

[hurk27]

If you have many 3-phase loads you might want to look at getting a 3-phase service installed, but like others said without a phase shift you don't have rotation just 180? reversal of sign wave from one leg to the other, if you only have a few loads, you can use a static phase converter to start the largest motor then with it running use it to also run the other motors, but if you are starting a high torque application such as an air compressor then you will need a rotary phase converter.

Here is a link for a few rotary PC's
http://www.americanrotary.com/products/phase-converters/rotary-phase-converters

And some reading material to learn about them:
Rotary

Static

 

[lakee911]

One might consider a VFD w/ a single phase input and a three phase output. Again, load determines if this makes sense.

 

[kwired]

One might consider a VFD w/ a single phase input and a three phase output. Again, load determines if this makes sense.

Or availability of three phase from POCO. There are a few 50 hp irrigation well motors around the area here with phase converters driving them. Not cheap, but same goes for running miles of line from the POCO.