Zigzag Transformers

Our Zigzag Transformers are designed for your grounding needs and can solve the grounding challenges you may be facing in your system

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All of our units are built-to-order, in either production-run or prototype quantities. Contact us with your specifications and we’ll get a design and quote the unit. If you don't know everything, we can help. Call us at US +1 408-263-8444, or email us by clicking the button below:

NRTL to UL icon These transformer are NRTL to UL 506 and 1561. Find out more about our certifications by clicking here: More on certifications

Build configurations and capabilities

Electrical Characteristics

Fault current

Fault duration

Continuous current

System voltage up to 15 kVrms

Frequencies at 50/60Hz

***Optionally, can specify X/R ratio + Impedance values

Terminal Configurations (Dependant on transformer specifications)

Copper buss bar

Silicon bronze hardware

Ring-lug compatibility

Touch-safe configurations

Lexan covers

Enclosures and weather

NEMA enclosures

NEMA 1: General purpose

NEMA 3: Weather-resistant (falling dirt, windblown dust, rain, sleet, snow, formation of ice)

NEMA 3R: Same as 3, omits protection against windblown dust

NEMA 4: Watertight

NEMA 4X: Same as 4, but stainless steel

NEMA 6: Submersible

Examples of Zigzag Transformers


370 kVA Zigzag transformer

3-Phase, 60Hz

System voltage = 400 Vrms L-L

CNC = 1,600 Arms in Neutral

ZPS = 0.0006 Ohms


5 kVA Zigzag transformer

3-Phase, 60 Hz

System Voltage = 480 Vrms

CNC= 18.3 Arms

ZPS = 0.52 Ohms ±1.1 Ohms


41 kVA Zigzag transformer

3-Phase, 50/60Hz

System Voltage = 480 Vrms

CNC = 41.1 Arms

ZPS = 1.4%

NRTL to UL 1561


Earthing transformer

3-Phase, 50/60Hz

System Voltage = 480Vrms

CNC = 360 Arms


About Grounding Transformers

The most common connection used in grounding transformers is the Zig-Zag connection. The grounding transformer is commonly referred to by this connection type, the Zigzag Transformer. Grounding Transformers are used for obtaining a grounded neutral on three phase, three-wire systems, providing a return path for zero sequence current generated by the loads in the system or by the fault currents. Sometimes a winding for auxiliary supply can be added besides the zig-zag winding.

Figure 1: Zigzag Connection

In a case of line-to-ground fault, sufficient current (3I) will flow through the neutral of the transformer, causing opposite current flow (I) in the zig-zag connected windings of the same core leg. This results in no magnetizing effect on the core and provides relatively low impedance from path to ground.

Grounding transformers are most commonly used for short-time operation (approx. up to 30 sec) during the fault currents. However, by connecting reactors they can operate continuously.

The basic parameters required for quoting a grounding transformer are: