How do I create a star- or delta connection?

How do I create a star- or delta connection?
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The three windings in our three-phase transformers have not yet been connected. This allows you – as the user – to arrange the circuitry in line with the relevant application. Discover the different options here.

A transformer always has two sides, the input or primary side (PRI), on the one hand, and the output or secondary side (SEC) on the other. You can also choose between two types of connection on each side: star (Y) or delta (?) . This results in four different connection systems:

How can I see that on the transformer?

To assist you in making the correct connections the various options are also indicated on a label , on each EREA transformer. The options for the primary side are shown on the left, with the secondary side on the right. The currents (in Amperes, A) are also shown. The new connections are indicated with stippled lines .

IMPORTANT: With the star connection you must also connect the neutral point (the neutral wire or neutral connector): this is indicated by N. This is done by connecting together the lowercase letters x-y-z (primary side) and/or u-v-w (secondary side).

Our three-phase isolating transformers are available in both the ‘classic’ SPT version and the energy-efficient SPT/BTE version.

And what is the position with SPT/D?

Only 230V delta is possible in the ordinary SPT series. In the SPT/D isolating transformer, however, EREA connect the primary side in a 400V delta , with no neutral conductor. This is particularly useful when a 3 x 400V IT system is available.

Just as with the SPT and SPT/BTE transformers, the SPT/D is available in an energy-efficient version , namely the SPT/D/BTE series. 

So what about ECT and PVT transformers?

As indicated in the table above, a star (Y=N) or delta (?) connection is possible on both the primary and the secondary side with the ‘ordinary’ SPT series. 

With the ECT and PVT isolating transformers EREA always connect the secondary side in a 400V star (Y+N) configuration. This type of connection on the secondary side is particularly useful in applications which specifically require a correct neutral conductor: Power supplies to charging stations for electric vehicles in a network without a good neutral conductor, and to link PV converters for solar panels.

As with the SPT and SPT/BTE transformers, an ECT/D version is also available.

EREA have, of course, provided these transformers with a modified label. So you can see immediately whether the primary and secondary side have already been connected in advance, or which connections can still be made: this is shown with the dotted lines.

A handy QR code

So you're looking at a transformer and you want to quickly see the available connection options. Simply scan the QR code. This will take you to the product page for your transformer. Scroll on via ’Product details‘ to ’Connection system‘ and open the PDF file. That's how we've made it easy for you.

Download our detailed white paper on the various connection systems here .

Still have questions about star- and delta connections?

Don't hesitate to contact us .

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