# How to tell if a transformer is wye or delta

• pyro214
In summary, the transformer schematics show two different configurations, one with two circles and one with four circles, which represents a transformer of either type. The first schematic shows a transformer that can step down voltage from three-phase to single or three-phase, with one of the two schematic configurations. The second schematic is for a transformer that can step down voltage from 440V to 115V, 24V, or 60Hz AC, with one of the two schematic configurations.
pyro214
I'm going through a list of 12 transformers and trying to determine if they are wye or delta. The schematics I have come across are for power engineering and don't go into too much detail other than the following:

The transformers step down ~400V 60Hz AC (three-phase) to ~120V 60Hz AC (single or three-phase) with one of the two schematic configurations:

1 - http://s8.postimage.org/66olvudat/transformer.png
2 - http://s8.postimage.org/edglnf3dh/transformer_4.png

I'm familiar with the first schematic drawing with two circles however this is my first time seeing four circles to represent a transformer; any ideas?

Thanks!

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The transformers step down 440V 60Hz AC (three-phase) to 115V 60Hz AC (single or three-phase), 24V 60Hz AC (single-phase)

How can 3 phase transformer step down voltage to single phase voltage?
3 phase transformer steps down 3 phase voltage to 3 phase voltage, the connection may be different between the primary and the secondary.

First you have to be sure that the transformer is 3 phase transformer.
Else if i didn't understand your point please correct for me what do you mean 440 v three phase to 24 v single phase.

I'm familiar with the first schematic drawing with two circles however this is my first time seeing four circles to represent a transformer

I think the four circles means that:
First circle -> input winding
The other 3 circles means there are 3 different outputs the transformer can give.

Do you have transformers and want to know there connections or you just have a schematic and want to know the connections?

How can 3 phase transformer step down voltage to single phase voltage?

Very easily, there are several ways.

The 'step down' bit refers to the change of voltage magnitude.

Plucking a single phase froma multiphase transformer involves
either a single winding (which has two ends and therefore a single phase)
or using the interphase voltage which is done to supply higher power devices in electricity supply.

So where you put the iron core of the single phase?
3 phase to 1 phase -> same secondary core will make the flux of the 3 primary windings path in the same core of the secondary resulting in 0 flux -> 0 voltage on the output.
BUT if you place the core of the secondary on one phase of the primary you will get an output but in this case you will have single phase transformer not 3 phase to 1 phase

I'm not a power engineer and I don't "know" the answer but it seems to me delta is normally used on the high voltage side of the transformer to avoid the expense of running a fourth cable. Wye is usually used on the low voltage side of the transformer in order to have a ground connection. This would be particularly important with a single phase output in order to avoid a floating circuit.

## 1. How can I visually tell if a transformer is wye or delta?

The easiest way to visually determine if a transformer is wye or delta is by looking at the transformer's wiring diagram. A wye transformer will have a star-shaped wiring diagram, while a delta transformer will have a triangle-shaped diagram.

## 2. Can I use a multimeter to determine if a transformer is wye or delta?

Yes, you can use a multimeter to determine if a transformer is wye or delta. Set the multimeter to measure resistance (ohms) and measure the resistance between any two of the transformer's primary or secondary terminals. If the resistance between the terminals is equal, the transformer is wye. If the resistance between the terminals is not equal, the transformer is delta.

## 3. Are there any other ways to identify if a transformer is wye or delta besides looking at the wiring diagram?

Yes, besides looking at the wiring diagram, you can also look at the transformer's nameplate. It will typically indicate whether the transformer is wye or delta. Additionally, you can also look at the transformer's connections. Wye transformers will have four or more wires connected to the primary and secondary, while delta transformers will have only three connections.

## 4. Why is it important to know if a transformer is wye or delta?

Knowing if a transformer is wye or delta is important because it affects how the transformer is connected in a circuit. The transformer's connection type determines the voltage and current levels that can be obtained from the transformer. Additionally, different types of loads, such as three-phase motors, require specific transformer connection types.

## 5. Can I convert a wye transformer to delta or vice versa?

Yes, it is possible to convert a wye transformer to delta or vice versa, but it requires rewiring the transformer. This should only be done by a qualified electrician as it can be dangerous and may void the transformer's warranty.

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