Combined transformer refers to a transformer and its high-voltage and low-voltage side switches and protective devices, which are assembled into a complete device at the manufacturer. Users can propose the transformer capacity specifications, number of high-voltage and low-voltage side circuits, electrical specifications, and measurement and protection devices that the manufacturer should provide according to their use requirements.
This type of combined transformer developed by an American electrical company is called a pedestal transformer in the United States, and its English name is Padmounted Transformer. It is called American box transformer in China. The fuse, multi-position ring network load switch, and off-excitation voltage tap changer of this transformer are installed in the transformer oil tank as components of the transformer. It is easy to replace the fuse or operate the load switch outside the oil tank to change the operating conditions of the transformer. The high-voltage side is connected to the circuit by an elbow-shaped cable head that can be plugged in and out with load. There is a low-voltage outlet box outside the oil tank, and the space inside the box can be equipped with protective devices and measuring instruments as required. All live parts are inside the box, and there are no exposed live parts.
Since the US 10kv system is YNyn connected, the transformer core is three-phase five-column; and China's 10kv system is Yyn connected, the transformers all use Dyn connection, and the transformer cores are also three-phase five-column.
