Zig Zag Transformer: Everything You Need to Know

Zig Zag Transformer: Everything You Need to Know

In today’s infrastructure, transformers are essential devices for transferring electrical energy through electromagnetic induction between circuits. They play a critical role in adjusting voltage levels, a key function in electrical distribution systems and power transmission networks. In this article, we’ll explore the zig-zag transformer, a special type among the various transformers.

What is a zig zag transformer?

A zig-zag transformer, also known as the “interconnected start winding”, is a special type of transformer that is designed to handle unbalanced loads and provide a neutral connection in three-phase power systems. It consists of three single-phase transformers connected in a zig zag configuration, allowing it to create a virtual neutral point for the system. This is particularly useful in systems where the neutral connection is not easily accessible or where unbalanced loads are common. The zig zag transformer also helps in reducing harmonic distortion and provides ground fault protection. It is commonly used in industrial and commercial settings where the reliability and stability of the power system are crucial. 

Zig Zag transformer winding connections

The Zig Zag transformer features a unique configuration with six coils, comprising three outer coils (ZIG windings) and three inner coils (ZAG windings). The interconnected star winding design involves linking the outer coil of one phase with the inner coil of the adjacent phase, forming a series connection between them. This interconnected star winding helps cancel out mismatch voltages as the windings in each phase have an equal number of turns but are wound in opposite directions. The inner coil terminals are connected to the neutral terminal, allowing the passage of zero sequence current components.

Specifically, the outer coil of phase ‘a’ is linked to the inner coil of phase ‘b’, the outer coil of phase ‘b’ is connected to the inner coil of phase ‘c’, and the outer coil of phase ‘c’ is connected to the inner coil of phase ‘a’. This interconnection introduces a 30-degree phase shift between the zig winding and the corresponding line-to-neutral voltage. Notably, the Zig Zag transformer has approximately 15.47% more turns than conventional transformers to achieve equivalent voltage magnitudes. While this design is effective for certain applications, it comes at a higher cost due to the increased number of turns.

Zig Zag Transformer applications

Grounding Transformer

Zig Zag transformers play a crucial role as grounding transformers in power systems, providing a reliable path for zero-sequence currents during unbalanced conditions or fault scenarios. By redirecting these currents away from the primary windings, Zig Zag transformers help maintain system stability and protect equipment, ensuring the safety of both the power infrastructure and personnel. Their ability to handle ground faults makes them integral components in power distribution systems where a robust grounding solution is essential.

Power Electronic Converters

Zig Zag transformers find applications to enhance performance and reduce harmonic distortions. Their unique configuration assists in mitigating harmonics, contributing to improved power quality. By providing a more stable and balanced output, Zig Zag transformers enhance the efficiency and reliability of power electronic converters, which are widely used in various applications such as variable speed drives, renewable energy systems, and other electronic power control systems.

Earthing Reference or Earthing Transformer

Zig Zag transformers are employed as earthing references or earthing transformers in power systems where a well-defined earth reference is critical. By connecting the inner coil terminals to the neutral and grounding the outer coil, Zig Zag transformers establish a stable reference point for the system’s earthing. This is essential for preventing floating grounds and ensuring the safety and reliability of the power system. The use of Zig Zag transformers in this context contributes to maintaining a consistent potential and minimizing the risk of equipment damage due to electrical faults.


Zigzag transformers are an essential part of our electrical infrastructure and can be employed as grounding transformers, power electronic converters, or earthing transformers.

At TTES, we have over 100 combined years of experience manufacturing, maintaining, and repairing Zig zag transformers and other types. If you’re looking for industry-leading lead times of just 20 weeks on average, don’t hesitate and reach out to us for a free quote!

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