The type DTW™ de-energized tap-changer is a versatile tap-changing switch, which is mounted inside the main transformer compartment attached to the cleat and lead structure of the transformer. The tap-changer is a modular design, which allows a wide variety of configurations to suit the needs of the transformer designer.
The tap-changer can be applied through BIL of 1,050 kV and has a base current rating of 1,000 A per deck. Each phase of the transformer requires at least one deck module of the tap-changer. Using multiple deck modules per phase extends the range of the tap changer to many different winding configurations.
Operation of the tap-changer is via a manual gearbox mounted on the exterior surface of the transformers. The switch is suitable for use as a dual voltage switch or as a delta-wye switch with appropriate modifications.