Non excitation magnetic strip tap changer for Distribution Transformer Applications

Non-Excitation Bar Type Tap Changer – Reliable Voltage Regulation for Oil-Immersed Transformers

Product Overview

The Non-Excitation Bar Type Tap Changer is a specialized voltage regulation device designed for three-phase oil-immersed power transformers. As an off-circuit tap changer, it operates exclusively when the transformer is fully de-energized, allowing for safe and reliable adjustment of the transformer's turns ratio to achieve the desired output voltage. This type of tap changer is also commonly referred to as a no-load tap changer (NLTC), off-circuit tap changer (OCTC), or de-energized tap changer (DETC).

Technical Specifications

This bar type tap changer is engineered for a wide range of medium-voltage applications. It is compatible with three-phase oil-immersed transformers operating at frequencies of both 50Hz and 60Hz, making it suitable for global power systems. The device accommodates rated voltages of 10KV and 35KV, and rated currents ranging from 20A to 250A. With such versatile parameters, this tap changer serves as an ideal voltage regulation component for small to medium-sized distribution transformers and power transformers in medium voltage distribution networks.

Voltage Regulation Modes

The tap changer offers two types of voltage regulation positions: central and neutral. The central voltage regulation mode adjusts taps positioned at the middle of the winding, while the neutral mode places the taps at the winding's neutral point. Both configurations provide effective voltage ratio adjustment, typically offering regulation ranges of ±2.5% and ±5% relative to nominal voltage. This flexibility allows the tap changer to accommodate different transformer designs and application requirements.

Mechanical Design and Installation

The bar type tap changer features a robust and straightforward mechanical construction. It employs a gear-and-rack transmission mechanism: when voltage adjustment is needed, the operator turns the handle on top of the switch, and the rotation is transmitted through the shaft, gear, and rack to move the moving contact assembly to the desired position. The moving contacts then short-circuit the adjacent fixed contacts to complete the tap change.

Installation is simple and versatile – the tap changer can be directly fixed on the transformer tank cover or tank wall. This direct mounting capability simplifies transformer assembly and reduces installation complexity, making it a preferred choice for transformer manufacturers and maintenance personnel.

Key Advantages

The bar type tap changer offers several significant benefits that make it a reliable choice for medium-voltage transformers:

• Simple and Compact Structure: The bar design features a streamlined construction that effectively utilizes the upper space inside the transformer tank, allowing for neat tap lead arrangement and balanced electric field distribution.

• Low Maintenance: Without complex switching mechanisms required for on-load operation, this tap changer demands minimal maintenance over its service life.

• Cost-Effective: As an off-circuit device, it is significantly more economical than on-load tap changers, typically costing about two-thirds of an on-load tap changer solution.

• Reliable Operation: The device delivers smooth operation with accurate positioning, excellent sealing performance, and low contact resistance.

• Safe Operation: Tap changes are performed only under non-excitation conditions (when the transformer is completely disconnected from the power grid), ensuring operator safety and equipment protection.

Typical Applications

This bar type tap changer is widely used in three-phase oil-immersed distribution and power transformers within 10KV and 35KV voltage classes. It is particularly suitable for applications where voltage adjustments are infrequent and can be scheduled during planned outages – such as in rural distribution networks, industrial dedicated transformers, and small to medium-sized substations. Once set during transformer commissioning, the tap position is rarely changed, making the non-excitation bar type tap changer an ideal and economical choice for stable power distribution environments.

Conclusion

The Non-Excitation Bar Type Tap Changer combines robust mechanical design, versatile voltage regulation options, and easy installation to deliver reliable performance for three-phase oil-immersed transformers. Whether used in 10KV distribution networks or 35KV power systems, this tap changer provides a cost-effective and dependable solution for voltage regulation in medium-voltage applications.