The minimum clearance required between side wall and the Main Switchboard is Most low voltage switchboards in Singapore need to be by undergo a series of stringent tests performed by an independent third party laboratory. UESTION 2 distribution transformer for a building is specified as 6.6 kVI415 V, 2 MVA, ONAN, YN11. Explain the term ONAN.

The term **ONAN** refers to a specific cooling method used for transformers. It stands for **Oil Natural Air Natural**. Here's a breakdown of what each part means: - **Oil Natural (ON)**: This indicates that the transformer uses oil as a coolant. The oil circulates naturally due to convection. As the transformer operates and generates heat, the oil absorbs this heat and rises, while cooler oil from the bottom moves down to take its place, creating a natural circulation. - **Air Natural (AN)**: This means that the cooling of the transformer is aided by natural air circulation. The heat from the transformer is dissipated into the surrounding air without the use of fans or forced air systems. The heat rises, and cooler air enters from the bottom, creating a natural airflow around the transformer. In summary, ONAN transformers rely on the natural circulation of oil and air for cooling, making them suitable for many applications where forced cooling is not necessary or practical. This method is commonly used in distribution transformers, like the one specified in your question.