Delta wye connection using 3 small transformers

In summary, the conversation discusses the correct wiring for a delta wye connection using three small transformers. There is confusion about whether to use X1 or X2 as the neutral connection in the wye connection. It is stated that the output voltage will be the same for both connections, but there may be a difference in phase rotation. It is recommended to use NEMA standardized connections and to label the higher voltage side as the line to line voltages on the high voltage side lead those of the low voltage side by 30 degrees electrical phase. The correct connections and phase labeling for a y-side and delta-side are explained, with the suggestion to connect the neutral to Earth ground if the y-side is a secondary. A sketch is also provided
  • #1
sauce6358
3
0
I am confused from a couple of diagrams I have about how to correctly wire 3 small transformers to form a delta wye connection. The transformers are labeled as
Primary H1 H2, H1 H2, H1 H2
Secondary X2 X1, X2 X1, X2 X1

My question is in all the diagrams I have the Delta connections are identical, but the wye connections in one of the diagrams shows all of X1's tied together to form the neutral and another diagram shows all of X2's tied together to form the neutral. So does it matter whether I use X1's as the hot connections and X2's as the neutral connections or viceversa?
THANKS!
 
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  • #2
Connecting all X2 together will give 3 phase output.
Connecting all X1 together will give 3 phase output.
There will be a difference of 180 degrees between the 3 phases depending on which connection is used. ?There may be a difference in phase rotation, will have to think about that?
The output voltage will be the same for both connections.
If you are using the output for a rectifier the connection will not make any difference.
If you are using the output for phase control, it may make a difference depending on the circuit you are using.
 
  • #3
Is the higher voltage side connected in wye? I would recommend using NEMA standardized connections. The industry practice is that the higher voltage side be labeled so as the line to line voltages on the high voltage side lead those of the low voltage side by 30 degrees electrical phase.

If the high side is in wye, low side in delta, here are the connections:

Y-side: Let us use "H2" as the neutrals. All 3 "H2" terminals are joined. Phase A hot connects to H1 of xfmr A, phase B hot connects to H1 of xfmr B, phase C hot connects to H1 of xfmr C. If this Y-side is a secondary, then it might be desirable to connect the neutral (H2-H2-H2) to Earth ground. It depends on the application. If the Y-side is the primary, then an Earth ground may already be present. Definitely check if you need to have the neutral grounded.

Delta-side: Connect X2 of xfmr A to X1 of xfmr B. Connect X2 of xfmr B to X1 of xfmr C. Connect X2 of xfmr C to X1 of xfmr A. Then label as follows.

The junction of xfmr A X1 & xfmr C X2 becomes phase A. The junction of xfmr B X1 & xfmr A X2 becomes phase B. The junction of xfmr C X1 & xfmr B X2 becomes phase C.

With these connections & phase labeling, the line to line voltages on the lower voltage delta side will lag those on the higher voltage wye side by 30 degrees, in accordance w/ power industry standard practice in North America. I.e. the A-B line-to-line voltage on the wye side leads the A-B l-l voltage on the delta side by 30 degrees.

If you're using the delta as the high side, let me know & I'll help you, as the designations would be different. Have I helped? Later, I'll attach a sketch.

Claude
 
  • #4
cabraham said:
Is the higher voltage side connected in wye? I would recommend using NEMA standardized connections. The industry practice is that the higher voltage side be labeled so as the line to line voltages on the high voltage side lead those of the low voltage side by 30 degrees electrical phase.

If the high side is in wye, low side in delta, here are the connections:

Y-side: Let us use "H2" as the neutrals. All 3 "H2" terminals are joined. Phase A hot connects to H1 of xfmr A, phase B hot connects to H1 of xfmr B, phase C hot connects to H1 of xfmr C. If this Y-side is a secondary, then it might be desirable to connect the neutral (H2-H2-H2) to Earth ground. It depends on the application. If the Y-side is the primary, then an Earth ground may already be present. Definitely check if you need to have the neutral grounded.

Delta-side: Connect X2 of xfmr A to X1 of xfmr B. Connect X2 of xfmr B to X1 of xfmr C. Connect X2 of xfmr C to X1 of xfmr A. Then label as follows.

The junction of xfmr A X1 & xfmr C X2 becomes phase A. The junction of xfmr B X1 & xfmr A X2 becomes phase B. The junction of xfmr C X1 & xfmr B X2 becomes phase C.

With these connections & phase labeling, the line to line voltages on the lower voltage delta side will lag those on the higher voltage wye side by 30 degrees, in accordance w/ power industry standard practice in North America. I.e. the A-B line-to-line voltage on the wye side leads the A-B l-l voltage on the delta side by 30 degrees.

If you're using the delta as the high side, let me know & I'll help you, as the designations would be different. Have I helped? Later, I'll attach a sketch.

Claude

Yes, Delta Primary Side and Wye Secondary Side. High/Low. Thanks!
 
  • #5
The attached pdf details how to obtain the industry standard high voltage side 30 degree phase lead using a wye-delta as well as a delta-wye xfmr configuration. I added polarity dots to the schematics as a visual aid. This should be what you are looking for. Hopefully it is legible.

Claude
 

Attachments

  • abraham_y_delta_phase_conn.pdf
    64.1 KB · Views: 299
  • #6
cabraham said:
The attached pdf details how to obtain the industry standard high voltage side 30 degree phase lead using a wye-delta as well as a delta-wye xfmr configuration. I added polarity dots to the schematics as a visual aid. This should be what you are looking for. Hopefully it is legible.

Claude

Thanks So Much! Sauce
 

1. How does a delta wye connection using 3 small transformers work?

A delta wye connection is a type of electrical connection that uses three transformers arranged in a triangular shape (delta) to connect three-phase power to a wye-shaped load. Essentially, the delta connection allows for three separate voltage sources to be combined to create a single voltage output, while the wye connection provides a common neutral point for the load.

2. What are the advantages of using a delta wye connection with 3 small transformers?

Using 3 small transformers in a delta wye configuration has several advantages. First, it allows for a more efficient distribution of power, as each transformer can handle a smaller load compared to using a single larger transformer. Additionally, the delta wye connection provides a higher level of reliability, as the load can still be supplied with power even if one of the transformers fails. This setup is also more cost-effective, as smaller transformers tend to be less expensive than one larger transformer.

3. How do you calculate the voltage and current in a delta wye connection using 3 small transformers?

To calculate the voltage and current in a delta wye connection, you will need to know the voltage and current ratings of each individual transformer, as well as the phase shift between the delta and wye connections. From there, you can use various formulas and equations to determine the overall voltage and current levels in the system.

4. Can a delta wye connection with 3 small transformers be used for different load types?

Yes, a delta wye connection can be used for a variety of load types, including resistive, inductive, and capacitive loads. The arrangement of the transformers allows for the voltage and current to be adjusted to suit the specific needs of the load.

5. Are there any potential drawbacks to using a delta wye connection with 3 small transformers?

While there are many advantages to using a delta wye connection with 3 small transformers, there are also some potential drawbacks to consider. One potential issue is the complexity of the system, which may require more maintenance and troubleshooting compared to a simpler setup. Additionally, the delta wye connection may not be suitable for all load types and may not be the most cost-effective option for smaller systems.

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