In the United States, the legality of using a microwave oven transformer (MOT) for wood burning would likely depend on local regulations and codes, as well as the specific application and modifications involved.
Modifying and repurposing electrical devices like microwave oven transformers can be potentially hazardous and may violate safety regulations. Safety concerns include the risk of electrical shock, fire hazards, and other dangers associated with improper handling of high voltage equipment.
It is important to note that electrical codes and regulations can vary from state to state and even within different municipalities. Therefore, it is crucial to consult with local authorities or a qualified professional, such as an electrician or fire safety expert, to determine the specific legalities and safety requirements in your area.
Additionally, keep in mind that if the wood burning activity involves releasing smoke or emissions, there may be additional regulations related to air quality or environmental concerns that need to be considered.
To ensure compliance with local laws and regulations, it is always recommended to seek professional advice from the appropriate authorities or experts familiar with the specific regulations in your area.