[Moved] Connections of a transformer

How can I connect three phase supply of 415 volts to 12 volts through a step down transformer?
I have a 3-input and 3-output terminal transformer.What are the various connections I need to make?

you need a AC or DC output finally?
for DC you can directly connect three phase bridge rectifier on output.

I think your transformer is delta to delta, can you post a image of it?

Venkadesh_M said:

you need a AC or DC output finally?
for DC you can directly connect three phase bridge rectifier on output.

I think your transformer is delta to delta, can you post a image of it?

Click to expand...

Hi,
I need an AC output of 12 volts. I don't have any image of my transformer. I just have a circuit in which this transformer is being used with the three phase supply. So if I connect two of the phases to transformer input,will I get the output of 12 volts? And I just wanted to know the difference when I connect single phase supply and three phase supply to the above mentioned transformer one by one?

Actually there are 4 configurations of 3 phase transformers. like delta to delta, delta to star, star to delta and star to star.

Without that info i cant answer you, but to say easily for delta input you need two phases input and for star in input you will need only one phase in input with one neutral.

by giving the power to only one winding you will also get the output in only one of three pins, if it is star output then against neutral and against another output pin if it is a delta output.

Venkadesh_M said:

Actually there are 4 configurations of 3 phase transformers. like delta to delta, delta to star, star to delta and star to star.

Without that info i cant answer you, but to say easily for delta input you need two phases input and for star in input you will need only one phase in input with one neutral.

by giving the power to only one winding you will also get the output in only one of three pins, if it is star output then against neutral and against another output pin if it is a delta output.

Click to expand...

Thanks for your reply.
What I did was I removed the same transformer from my circuit and connected it with my home supply of 230 volts single phase, now also it gave me 12 volts AC output? Can u tell me what type of transformer am I using?

It is a difficult question. can you make some diagrams about your connection? please don miss the not used wires. assume transformer as a box.

or take a photo and post here.

Venkadesh_M said:

It is a difficult question. can you make some diagrams about your connection? please don miss the not used wires. assume transformer as a box.

or take a photo and post here.

Click to expand...

Here it is,

You will get 7V.

If you want to know how, it is 12/√3.

three phase transformer

What will happen if I supply two phase as input to a three phase transformer?And also when I connect single phase supply to the same transformer?

Re: three phase transformer

The answer depends on the transformer winding circuit (can be wye, delta or zig-zag), also on the phase relation of the "two phase" input.

In most cases no good result.

Re: three phase transformer

amanpreetk said:

What will happen if I supply two phase as input to a three phase transformer?And also when I connect single phase supply to the same transformer?

Click to expand...

It will be inbalanced.

You cannot generate 3 phase from 1, nor 2 from 2 complementary voltages. Which is still 1 phase of 3 with a centre tap.

a loss of one phase of 3 creates an inbalanced vector output which may harm 3 phase machines.

Re: three phase transformer

Are you talking about this https://www.edaboard.com/threads/324460/

can you be more specific ?

Thanks for pointing out the duplicated thread. Merged both threads.

Re: three phase transformer

Venkadesh_M said:

Are you talking about this https://www.edaboard.com/threads/324460/

can you be more specific ?

Click to expand...

Hi,
Yes I am talking about the same transformer.I got to know a few more things about the transformer.
Today I tested my transformer using two of the phases as input, I got the output around 14 volts,
And then next I supplied it with single phase supply of 230 volts, it gave the output around 7 volts, i.e. exactly half the value which I had got using two phases as input.
Still I am not able to judge what type of transformer is it?
Actually I want to design a circuit in which I need to check the presence of all the three phases?

- - - Updated - - -

Venkadesh_M said:

Are you talking about this https://www.edaboard.com/threads/324460/

can you be more specific ?

Click to expand...

Hi,
Yes I am talking about the same transformer.I got to know a few more things about the transformer.
Today I tested my transformer using two of the phases (from three phase)as input, I got the output around 14 volts,
And then next I supplied it with single phase supply of 230 volts, it gave the output around 7 volts, i.e. exactly half the value which I had got using two phases as input.
Still I am not able to judge what type of transformer is it?
Actually I want to design a circuit in which I need to check the presence of all the three phases?

Still I am not able to judge what type of transformer is it?

Click to expand...

Never worry about the type of transformer. whatever its type just assume it as a black box. Now two inputs two outputs.
Lets take input voltage as V1 and output voltage is V2

V1/V2 is always a constant.

for example when you give 230V in the input, you got 7V in output

so the constant is 230/7 = 32.8

so when you are getting 13.5V the input is 32.8 * 13.5 = 444V between two phases

We are having first phase as 230V so the Voltage in the second phase is 255V.



I don think that was possible so there must be some mistake in the experiment otherwise you will get 12V when giving two phases.

https://www.1728.org/vectors.htm

Actually I want to design a circuit in which I need to check the presence of all the three phases?

Click to expand...

There are lot of ways doing this. If you want this as a product also there are lot of products available they will be called single phasing preventer. They will also include phase sequence.
If you want to do on your own, then you have to study a lot about 3 phase voltages and their characteristics.

Venkadesh_M said:

Never worry about the type of transformer. whatever its type just assume it as a black box. Now two inputs two outputs.
Lets take input voltage as V1 and output voltage is V2

V1/V2 is always a constant.

for example when you give 230V in the input, you got 7V in output

so the constant is 230/7 = 32.8

so when you are getting 13.5V the input is 32.8 * 13.5 = 444V between two phases

We are having first phase as 230V so the Voltage in the second phase is 255V.

View attachment 110328

I don think that was possible so there must be some mistake in the experiment otherwise you will get 12V when giving two phases.

https://www.1728.org/vectors.htm


There are lot of ways doing this. If you want this as a product also there are lot of products available they will be called single phasing preventer. They will also include phase sequence.
If you want to do on your own, then you have to study a lot about 3 phase voltages and their characteristics.

Click to expand...

Thanks a lot for your reply,it realy helped me.
Can you say anything,whether the transformer is single phase or three phase? And if it is single phase transformer,can I apply two phases to it? Or if it is three phase, can I supply it with two phase as input?

whether the transformer is single phase or three phase?

Click to expand...

By counting the terminals and number of windings anybody can tell.

if it is single phase transformer,can I apply two phases to it?

Click to expand...

No. Every transformer is limited for maximum voltage. It will affect the transformer in terms of core saturation and puncturing the insulation.

if it is three phase, can I supply it with two phase as input?

Click to expand...

Yes for sure. but the voltages in each outputs are a chapter to explain about.