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Zigzag Transformers for Special Applications

Zigzag transformers have windings arranged in a zigzag configuration that allows them to be used for special applications. They can be used as an autotransformer with no isolated circuits or in a two winding configuration to provide voltage transformation and isolation. Zigzag transformers are more effective for grounding purposes in ungrounded power systems compared to wye-type transformers because they have lower internal winding impedance to ground.

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1K views1 page

Zigzag Transformers for Special Applications

Zigzag transformers have windings arranged in a zigzag configuration that allows them to be used for special applications. They can be used as an autotransformer with no isolated circuits or in a two winding configuration to provide voltage transformation and isolation. Zigzag transformers are more effective for grounding purposes in ungrounded power systems compared to wye-type transformers because they have lower internal winding impedance to ground.

Uploaded by

klaus muecher-erskine
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOC, PDF, TXT or read online on Scribd
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The Basics of Zigzag Transformers

These transformers have special windings, appropriate for special applications.


You can interconnect transformer windings in several ways to produce various output
voltages. For power and distribution, you employ the conventional delta or wye
connection. But for special applications, you can use another lesser-known
configuration: the zigzag connection.
You will typically find the windings on each phase of a zigzag transformer in two halves.
These winding halves interconnect to obtain a zigzag arrangement.
You can use the zigzag connection as an autotransformer, serving as the primary and
secondary with no isolated circuits. The common portion of an autotransformer (low
voltage) is the common winding, and the remainder is the series winding. (Together
these make up the high voltage side of the transformer.) You can use the zigzag
transformer in two winding transformer applications, where you obtain voltage
transformation and isolation with the zigzag feature.
If you need a neutral for grounding or for supplying single-phase line to neutral loads
when working with a 3-wire, ungrounded power system, a zigzag connection may be the
answer. Due to its composition, a zigzag transformer is more effective for grounding
purposes because it has less internal winding impedance going to the ground than when
using a wye-type transformer.
In ungrounded systems, it's still necessary to detect a ground fault. With the zigzag
transformer, you typically insert a resistor between the neutral point and ground to limit
ground fault current on the system.
You can also use the zigzag connection in power systems to trap triple harmonic (3rd,
9th, 15th, etc.) currents. Here, you install zigzag units near loads that produce large
triple harmonic currents. The windings trap the harmonic currents and prevent them from
traveling upstream, where they can produce undesirable effects.
In the past, we used half-wave rectification circuits for producing DC voltage. However,
these DC currents often caused transformer saturation. With the zigzag connection, the
currents in the two halves of the windings on each leg of the transformer flow in opposite
directions, avoiding saturation.
We rarely use zigzag configurations for typical industrial or commercial use, because
they are more expensive to construct than conventional wye-connected transformers.
But zigzag connections are useful in special applications where conventional transformer
connections aren't effective.

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